Clio 1.5 dci injector problems?

My 2004 clio has recently been showing up the stop, coil and engine management light! All 3 icons at the same time, my mechanic put it on the diagnostic computer and it read fuel pressure. He replaced the fuel filter but the car is no better and the engine sounds awful. He has checked the injectors and quoting me £75+vat for each injector....I need all 4! Then I need a fuel pump and the tank cleaned. He says this is a big job which will cost around £600-700 before he even looks at my car for mot which needs a few things. And tells me it'd be better to scrap the car? The whole car is immaculate condition. Anyone know anything else it could be? Before I lose out on lots of money ***128557; the cars only worth about £1000 and has 110,000 miles on the clock.