Thanks again for all your comments, I have now bought one - I will tell you about my day, you couldn't write this!
We left home about 2.00 pm headed for Trago Mills at Newton Abbot, as we had to pass Exeter which was where this car was I thought we would go and have a look. It was on the Sowton industrial estate - for anyone who knows it. We eventually found the place and the car but couldn't find out which unit it belonged to - and I didn't have the phone number. The car didn't look to bad at all, a few dings and scratches but I have seen a lot worse. After enquiring in several units I found the owners.
I had a look round it, checked for head gasket leakage and gave it a general inspection, took it out for a drive and it went very well with no obvious problems. When we came back I checked for cooling system pressure and was pleased to find there was none - I took the oil filler cap off and there was a timing chain - this car was supposed to be a 2.0L LX, anyway with a bit of haggling I got it for £300.00 with three months tax and MOT, we wanted to get to Trago's so I said we would pick it up on the way back, then the wife reminded me that I hadn't left my details, we just managed to get back about 5 minutes before they closed and did the paper work when it indeed proved to be a 2.2L but I thought at that price if it lasts until the MOT runs out it would be worth nearly that for scrap. Looking at it in the car park I also noticed it was an SX.
So we left, Christine behind me in the 406, to get to the A35 you have to travel along a short section of the M5, half way along it stopped and wouldn't start, this is in the rush hour, as it was approaching the slip road the C5 was partly projecting into the n/s lane, I phoned the AA and to their credit the had a recovery truck with us in about seven minutes, they took the car into Exeter services where we met up with them, I was informed that a patrol was on the way to check it out, by this time I would have been quite happy to leave it there and go home in our nice 406 that works.
I was told that the patrol would be there in half an hour so to go into the services and have a drink, which we did, I hadn't even poured out my tea when the phone rang to say the patrol was with the car so I abandoned my refreshments and went outside. The AA man pronounced that it was out of fuel

although the gauge was showing a little, on every other Citroen I have had the fuel has lasted until long after the needle has hit the stop. The mechanic asked if I had bought it on ebay - he said 'we get a lot of this'
From then on it all went fine, it drives very nicely, I couldn't check the fuel consumption as I haven't worked out how to use the computer yet. The first job will be to put some tyres on it as I'm not sure they are all legal, the first thing I thought of when I stopped on the motorway was that Mr Plod will be along in a minute but fortunately the AA van turned up first, there was also the insurance issue, once I had paid it was officially mine but fortunately it still had any driver cover from the firm I bought it from which was not a garage.
I dare say a number of faults will surface as I drive it, I will keep you informed, the first is to find out what is running the battery down - after I've put some tyres on!
Peter
P.S Don't tell them on the XM club