I did a lot of research on air compressors and had a chat with a colleague who used to service them. His basic advice was to get a 50L model with twin piston. More interestingly, he said that Abac make most of the re-branded compressors for the likes of Sealey, SIP, NuAir, Rockworth, Draper, etc. If you look at these, they are all the same motor, pump and tank, just in different colours and with very different price tags!

Sealey 50lt V-Twin Compressor 3hp 11.6CFM SAC5030VE *F.O.C. NEXT DAY DELIVERY!* | eBay
SIP 06242 AIRMATE TN3.0/50-D 3hp 50 Litre V TWIN AIR COMPRESSOR 50L tool gun | eBay
Burisch Air Compressor 3HP 50L 50 ltr litre 14CFM V-Twin NEW | eBay
50L 50 Litre Air Compressor 230V Draper 2.2kW V-Twin Air Compressor 3HP 116PSI | eBay
Air Compressor 3hp 50lt Twin V Motor 230v SUPER QUALITY | eBay
SIP (S.I.P) 05287 Airline VDX/50 CM3 Air Compressor 3hp 50Ltr Twin Piston | eBay