Fords are better than in the US, also all the GM cars are better (vauxhall/opel). The various small VW models that are not sold in the US are very good cars. SEATs have VW chassis and engines, but they do not hold their value as well. Like EJ25 said, the french cars are not famous for their quality. Anything italian though (alfa romeos, lancia, fiat) is complete shit. Im not sure about MG and other english cars. I would stick to japanese or german.

Im also not 100% of the laws in the UK but they are probably as the same as the rest of the european union, tax is based on the size of the engine. Thats why you will find a lot of turbocharged 4 cyl models.