• Bombardiere - Mainly older buildings, particularly 18th-century style London buildings
• Rivit- A Flying Scotsman mod for the default SC4 train, as well as some nice UK style sports pitches
• mattb325 - A plethora of buildings from Britain which are essential for any UK city builder. Plenty of Australian and Canadian buildings too which will fit in with a UK style (check out his SC4devotion uploads too)
• davide1983it - a nice row of Liverpool terraces and other small bungalows that may fit in a British city
• dragonsteincole - an incredible array of modern British trains for your city
• TheGazJones - has created a pack of British corner shops
• justforfun
• WannGLondon  has created a set of London style flats
• ILL Tonkso - An absoloute MUST for British themed cities
• frogface - Another MUST for British themed cities
• Gascooker- over at SC4devotion, an incredible amount of British themed content
• rsc204 has some excellent British supermarket Lots
• mntoes - mostly UK suburban homes
• callagrafx - Old English/modern London architecture

I'm sure I have missed loads of other users out, so please feel free to add or send me any names via a PM.

Happy Building