The 1.5 Dci Clio is a great little car for cruising up and down motorways, you should have no problems.
Firstly you need to check a couple of things :
1) Does the car have service history?
2) Has it had regular
changes ? (most important on a diesel)
3) Does it smoke on start up ? (any colour smoke)
4) Look at previous MOT's for problems. (you can do this on the net too)
5) Look for signs of accident damage.
6) If buying from a trader will he give you a warranty ?
7) Has it had a cambelt change ? (very important)
Hope this helps, there should be loads of information on this site and if not ask ask ask.......