If you're happy patching and splashing then I'd do so. However, in the grand scheme of things, I'd weigh up the cost against the cost of a replacement vehicle, and against the knowledge of everything else you've done to the car.
I spent £500 last year getting a car worth £500 through the MOT. However, I know the car, recently done brakes, tyres and exhaust and expect to get at least another 12 months out her. I could get a replacement for £500 but then have all the unknowns and could be faced with another bill in a months time....
