I had the fuel pump go on mine, and I'm sure I had random issues before it went.

The pump cost about £100, and I paid a garage to fit at another 100 quid. Sadly, the garage didn't actually attach the fuel lines properly, and I developed a major fuel leak.

I fixed this with a mate, by dropping the tank and fixing the lines in properly.

Wasn't too bad a job - lower exhaust, take off part of the heat shield, and drop the tank by releasing the metal straps that hold it. The pump housing just twists off.

EDIT: Also a 1.6 Focus (02 Plate)