Got around £30 to spend on a stem – the gussett staff looks a good bet. Any experience?

I have one and it holds my bars in place.

Yep, mine is light and so far has not snapped in half. Well finished too.

do they all come with spare face plates/shims?

yep does the job, comes with 2 faceplates, is cheap, looks good
I would also recommend a Pro FRS – http://www.tredz.co.uk/.Pro-FRS-Alloy-Stem_30056.htm
Have both, of the two I prefer the Pro, seems better finished and tidier, nicely rounded shape around the steerer clamp bolts

aye – had the pro last in 50mm (was ace) and would probably go for that again if i can find a 70mm with some rise

Pro is good, aye… Though both of mine have the logos on squint, to me they look cheaper than the Staff and the finishing’s pretty iffy. Lower stack than the Staff and generally more compact. Still they’re both cheap and they work.