Update. I traded the Cinq for a cambelt kit and alternator belt.
Car has now done 4500 miles and does on average 65mpg. This was from 55mpg before I changed the air filter. I have bodged the driver seat for the time being so now it only moves a little rather than loads.
That's it. That's all I have done to it.
Planned for end of month is a two new tyres. Spare has no tread at all and rear right looses 15 psi through the course of the day.
New handbrake cable and throttle cable, oil and oil filter change and possibly new shock for the front.
Next time my dad comes round I will get him to weld the seat mounting.
Very economical car. I was amazed last time I filled the tank it had done 71mpg.