Well, u may have some very old parts on ure car at the mo - Old gasketts,filters, motors, etc. The best thing to do if you want to keep it running is to get a new fuel filter (about 8quid if that) vrey easy to fit, which should keep ure engine being supplied with the cleanest juice possible. Then make an oil change - make sure yours isnt black coz then you really have to change it! Check all your fuses to keep your electrics working. Make sure your cam belt is in good shape coz judging by your millage (unless uve changed it recently) it could be in a state and you really dont want that snapping.
All of these things (bar the electrics) would adversly affect performance if not adhered to............... There are lotsa other none expensive things you could do.... P.S Sorry if you know all this!!!