you're not gonna get 400bhp from a td05 or 440 injectors
350bhp in a classic will be a rapid car, don't go chasing figures and willy waving. timg has got a classic wagon with 330bhp and there's not much that will keep up with him
if you do want 400bhp, it will be cheaper to sell yours and buy one that someone has already spent loads on
if you want to do it yourself, not sure how strong your engine block/clutch/gearbox are on yours, but, £800+ for turbo, £200+ for injectors, £500+ for motherboard and mapping