I had pretty much the same problem last year on my (then 5 year old) mower, but it wouldn't drive in forward or reverse . My local Countax service centre told me that the gearbox needed replacing and he hadn't come across this problem with Countax before. Having previously owned a Westwood for more than 12 years, with very few problems, I am extremely dissatisfied with the Countax. Every season I have some problem or other with it - I went to start it today and the battery was flat! I'd try to sell it on eBay, but I don't think that I could be that cruel to some unsuspecting punter, good luck with your problem - you're going to need it.
Tony
April 2006