You will have to have a general medical every year to keep a class one current. This costs around (i think) £100 and varies depending on where you have it done.
The other tests like chest X-Ray, ECG etc are repeated about every 5 years, I can't remember exactly what the time frame is with out looking at my class 1.
Hope this helps.
[This message has been edited by Capt Wannabee (edited 17 April 2001).]