Hi Jon,
with regards to your projects, then they all appear to be worthwhile additions/changes, each of which have been tried with various success over the years, so there are various threads on the forum for guidance - you won't have to make any leaps into total darkness, byt may wish to add your own ideas to what has gone before - nobody on here (well, me anyway) knows everything, and there are always new ideas - which I welcome.
I make a few observations here, which you can take or leave as you see fit - it's YOUR car, you do what YOU want, and good luck.
• Make a hard top
Not sure how easy it is to make from scratch, or convert an (MGF?) one. • upgrade front brakes (hispec or wilwoods)
Many find it a great improvement (even if just in confidence levels), but i still reckon OE ones in GOOD CONDITION, with good tyres fitted, are plenty good enough. • add some cup holders ( I like my morning coffee)
Not sure of the S2, but in the SE, a 'standard' Costa cup (plastic re-fillable one!) sits nicely between the arm rest and the rear bulkhead - never had a spillage yet. • put the loose parts of the dash back together ( I understand this is pretty common)
Get the glue out! • improve the sound system ( who needs a cd changer now days)
Lots of people have spent big money, many have spent less, I spent £30 on a unit from Lidl!!!! But I'm deaf in one ear and only drive with the hood down (unless it's really raining), so any more would be wasted on me - each to their own • make myself a wind deflector
Well worthwhile • possibly get a roll bar made
Even more worthwhile • new wheels, as I'm not keen on the S2 BBS wheels
I'll take the S2 BBS ones off your hands for £50
• Elise S1 style front fog lights/DRLs
Not my sort of thing, but hey, as I said, if it's what you want, then go for it.
Most importantly, if you can't find the answer to anything you want/need to know - just ask.