Rich,
We still have our Esprit; presently also own an Elise SC and a Cup 260
Previously we have had a 2002 111S 160 (Rover engine 156bhp), then a 2004 111R (Toyota engine 189bhp) trick second cam at 6K although some have had ecu upgrade lowering second cam switch to 5K also Toyota engine cars much cheaper on servicing, think the road tax is pretty good as the CO emmissions are pretty good
The later S upto a year ago or so the 111S Toyota was a 1.6ltr about 135bhp i think these are now 1.8ltr
To be honest if you want an everyday car and occasional track fun go for the 111R anything less in the power stakes you will feel cheated (being an ex Esprit driver) you should be able to get a good 111R for your £15K; your best bet is going to a dealer who has a few different bhp models in and have a drive in each
If you want more track days than everyday userbility then an Exige S2 (190 early cars then 220/240 upto 260 (257bhp) awesome fun both on the track and on the road; if split is roughly 50/50 then an Elise SC (218bhp) but you may need a bit more money but believe me well worth stretching the bank!!
KR darryl