Disclaimer: Intended to be played on Survival mode, not only for the increase in difficulty, but mainly due to ammunition weight changes being part of the rebalance.

Ammo changes:
Damage has been mostly normalised to calibre. The maximum damage of each calibre from standard (non-unique) weapons WITH weapon modifications and WITHOUT player perks (SA = semi-auto, A = auto):

Ammo                    Damage (SA/A)
.32                          20/30
9mm                      25/35
.45                          30/40
.455                       100
5mm                      25
.280                       30
.303                       60/100
.50                         150
HE.50                    250
2mmEC                 200
Shotgun Shell       90
Explosive Shell     200
.38Tround             40
Simplex Tround   40
Cell Tround           ?
Lead ball               150
Cannonball           500
Railway Spike       100
Cell                        50/120
Fusion Core          25/100
Plasma                 100
Gamma                 ?
Alien Blaster         200
Flare                      50
Cryo Cell                ?
Flamer Fuel           20/40
Shaped charge     400


Weapon changes:

.32 Pistol: reduced damage (almost halved), slightly reduced weight.
9mm Pistol (Luger): reduced weight, slightly increased value.
Chinese Mk 1 and 2 Pistols: increased value of both, slightly reduced damage of Mark II.
Covert: reduced weight, left ridiculously high damage (for .32) as is.
Crude Revolver: increased damage of longer barrels, increased damage and recoil of .45, .303 and 12ga receivers.
Service Pistol (Webley 1913): greatly increased damage and value, increased recoil.
Service Revolver (Webley Revolver): increased value, increased recoil.
Bulldog: changed calibre to .455, increased damage, value, weight and recoil.
Ferryman’s Friend: increased value, decreased weight.
Iron Curtain: changed calibre to .455, increased damage, value and recoil.

Combat Shotgun: slightly increased value and recoil. Switched slug receiver to explosive slug, since there are no 12ga slugs in the game, but we do have explosive slugs.
Crude Shotgun: decreased value (it’s a pipe).
Double-Barrel Shotgun: slightly increased damage, increased recoil.
Fire-Lance Shotgun: increased recoil.

Crude Sniper Rifle (HAMR): reduced .32 receiver damage and recoil, increased .303 and 12ga damage and recoil, switched Dragon's Breath receiver with standard .50 receiver alongside existing HE.50 receiver and increased their damage and recoil.
Musket: slightly increase damage and recoil.
Railway Rifle: increased weight of weapon and ammo, increased cost of ammo (to counter balance the high damage and recoverable ammo).
Service Rifle (Lee Enfield): slightly increased damage, value, weight and recoil.
Tround (Dardek): increased damage of longer barrels, increased value.
Vintage Rifle: slightly increased damage, increased recoil.

Angel SMG: slightly increased damage, increased value. Less damage than other SMGs, but has less recoil and faster rate of fire (high-tech Angel recoil-reducing mechanism, maybe).
Box SMG: increased damage, slightly reduced weight.
Crude Gun (Crude Blowback): reduced weight, greatly increased .303 receiver damage and recoil.
Ramshackle SMG: increased damage and value, reduced weight, slightly reduced recoil.
Sterling SMG: slightly reduced weight, increased recoil.
SMG (Sten): increased value, slightly reduced weight, slightly reduced recoil.

Battle Rifle (FN FAL): reduced damage of 5mm receiver and increased damage and recoil of .303 receiver. Intended to be a lightweight 5mm and .303 alternative to the LMGs, but with more recoil.
Combat Rifle: slightly increased recoil.

Light MG (Bren): increased damage, value and weight. Deals the most damage of the LMGs.
Lewis Gun: slightly decreased weight (still heavy), decreased 5mm damage, increased .45 damage and increased .303 damage. The most controllable of the LMGs.
Heavy MG (MG42):greatly increased damage, and slightly increased recoil. Highest RoF and DPS of the LMGs (and pretty much the most powerful weapon in the game), but is hard to control (.303), and eats through ammo.

Crude Laser (Zap Gun): slightly increase value. Increased weight of fusion cores, and greatly increased their value/cost, and the fusion core conversion was way too efficient/overpowered.
Gauss Rifle: increased value and weight, since it is comically powerful.
Plasma Pistol: left as is.

Broadsider: greatly increased weight and damage. Increased weight of cannonballs, and fixed cannonballs not appearing as loot from Jack Tars wielding the weapon.
Flamer: increased value, slightly increased energy damage and reduced radiation damage of herbicide receiver.
Bow: slightly increased damage.


Enemy changes:
Increase health of Famished, Wombles, Gehennas, and Mittenlurk Queens (intended to be mini-bosses that soak up a lot of ammo).
Gave ghouls radiation immunity (for some reason only legendary ghouls had radiation immunity).


Miscellaneous changes:
Increased resource cost of most ammunition crafting recipes, and added recipe to craft cannonballs.
Increased value of Photon Brew.
Nerfed a certain companion perk (from 50% increase to 20% increase).


Some recommended mods:
Unlimited Survival Mode - F4SE - I prefer to re-enable saving without sleeping.
Survival Configuration Menu - I prefer to remove adrenaline and diseases.
Bullet Counted Reload System (BCR)
Tactical Reload
Fallout London - Animation Fixes -Tactical Reload - BCR
Manual Reload - F4SE
always climbable ladders
Bren Gun Sound Fix
Lewis Gun Barrel Sound Fix
Fallout London Item Fixes
Leveled Item Fixes (LIF) - Fallout London Edition
Fallout 4 London - OMOD Fixes
Local Leader Tweaks Redux
Local Leader Tweaks Redux FOLON