If the car has a full years MOT it will achieve a better price. People know they can drive the car for a year without any worries of additional expenditure.
How much you've spent on the car previously doesn't mean alot really on such an old car but adds some piece of mind. When selling a car, I always put all the documenation into a ring binder, presents it nicely and makes it look like you care (even if you do not!)
It is certainly worth ensuring the car is clean and tidy, give it a good polish and wax, tyre black, vaccum the inside and use some air freshner and stuff like that. Throw out sticky toys and any crap in the car. Presentation when selling a car is very very important more so than how mechanically sound the car is in most cases. If there are areas of rust, treat them, this will detract from the value.
If the car is taxed you should add that to the value of the car or do a deal with the buyer, because that could be worth more than the car.
I would probably agree with Peter on the price. If it is a nice example, few owners, well maintained, clean with a long MOT it could double the value. These cars are as cheap as chips making them an ideal buy for people looking for cheap motoring.