Please Help! AEG dishwasher not cleaning properly

Hiya, hope someone out there can help me! My AEG Favorit 5040 is quite old (got to be at least 10yrs old!) but it has finaly started playing up! It started by not cleaning the top basket properly - came out with a 'grit' stuck to the bottom of the cups. Not always or on every wash or even in the same area of the basket so assumed the top arm was blocked or not spinning properly. Cleaned it all out, carefull with loading, problem got worse to the point out of one load, half the load would need to be redone. Now it has started on the bottom with the plates. Now I have cleaned it out to within an inch of it's life, the filters, the rotary arm, but its getting worse. I appreciate it is old but I can't afford a new one and when I rang a local repairman for advice, I was promptly told that he was not an advisory service and it would cost me £60 for him to come and look and then he could tell me if it was worth repairing it !! So is it or do I have to resign myself to christmas without a d/w and 6 people in the house, while I try to save for a new one , or it is something I can have a go at fixing myself? I'm hoping it is something pretty simple and pretty inexpensive to repair so any help or advise would be really appreciated! Thanks for your time

Is it heating? Are the spray arms actually rotating?
Heating you can easily check. To check if the spray arms are rotating open the door carefully during a wash cycle & set them both pointing directly towards you. Close the door, wait a few mins then open it to check if they have changed position. If the machine heats, the spray arms rotate, & everything is as thoroughly cleaned as you say then I would suspect the wash motor isn't functioning correctly. You'll have to post the machine pnc number on the door lip if you need further information.
You know you can't really blame the service engineer...he isn't a free advisory service & without accessing your machine he can't tell you exactly how much its likely to cost. Car salesmen don't give away free cars...why should a service engineer help you for nothing

yes it is heating and the rotary arm is moving.
Please don't misunderstand me, I would be quite happy to pay an engineer to come out and take a look and I would not expect him to know immediatly what is exactly wrong unless he looked, but only if he appeared to have an idea of what was causing the problem! When I phoned for his advise and asked if he had any idea of what was likely to be the cause he was rude, abrupt and then told me he was not an advisory service! It was his manner that I am unhappy with - My husband is an Electrican, and people often ring with the 'I'm not sure why, but this is what's happening - do you have any idea?' and he is happy to give an idea but obviously cannot give an exact cause or cost until he sees the problem, and then he can advise and fix. I just think that common courtesy and the reassurance of knowing something of what you are talking about goes a long way!
I sincerely appreciate that you have suggested i 'try this, could be that' and that was more of what I would hope for from an engineer who could reasure me, then I would have been very happy to have him come over and take a look
I'm sure he's just an odd one in the bucket so maybe I will try another!

Thanks for your suggestion though, I really appreciate you taking the time to write.