The flexi extension used was similar to this one - [url http://cgi.ebay.co.uk/LASER-QUICK-CHUCK-EXTENSION-FLEXI-300MM-3412_W0QQitemZ320281315636QQcmdZViewItemQQptZLH_DefaultDomain_3?hash=item4a92410934&_trksid=p3286.c0.m14] [/url], this ones a bit longer than mine so should be better to work with, I would also think that cheaper could be found elsewhere.
Yip I would think that the engine size and gearbox type would be the two main factors in getting the right part also if you have your chassis number handy the part that would be fitted to your car will be easier to identify - my car has the same engine and gearbox as yours on a year 2000 plate so I would imagine that yours would be the same as mine, the part number for mine is 0273 004 206 I took mine off to be sure, also the car will still drive with it off, you'll just have no ABS, TC, power steering or speedo but at least you'll be aware that they aren't working instead of them failing without warning.
The reason yours is ok at times is due to the connections making and then breaking contact due to vibration/corrosion, eventually they'll break contact permanently.
Hope this helps.