One sold a few days ago, here on the BBS. Mk1 £250 in what I'd describe as very good condition.
Another 124 sold at the recent Melbourne Fayre vgc-exc £210. (Mk1 or 2?)
Which hopefully gives you some idea.
As ever, the more verifiable info the better eg. Condition (especially safety catch on a Sport), any paperwork (servicing or parts receipts), chrono results and photos all help in both getting a decent valuation and achieving the best price. HTH