I've done a couple of similar projects - weight weenie on a shoestring. The last few grams always end up costing the most! M751 cranks are a good choice and the matching ES71 BB is also lightweight. M752 are a tad lighter and have a nicer shape IMHO than the 751. Weight-wise you can get similar results from an M570 with a UN7x BB.
A couple of other recommendations for £/g savings. Grips-wise, these £4/25g foam ones from ebay: http://www.ebay.co.uk/itm/25g-Ultra-Lig ... 1087520199
. If you have a standard-ish size seatpost size, these are £17 and ultralight: http://www.cyclomonster.com/cart/gub-li ... -post.html
For wheels, I'd avoid Shimano hubs for weight-saving, and if Mavic-rimmed go for 517s if possible. I've got hold of a couple of sets of 1st Gen Mavic Crossmaxes SUP (one set 1546g, the other 1596g), but in decent condition they fetch a lot. Also the 1st Gen Mavic Crossrides are pretty light. I found that cheaper second-hand options are Rolf - 'Propels' about 1600g and 'Dolomites' about 1750g ('Satellites' are heavier though).
Tyres? The reason I ended up at this thread - Exeter Man pointed out you might be interested in my Maxxis 330s currently for sale: viewtopic.php?f=39&t=247660
. [Though they are now sold, and I also realised I'd already sold you some Schwalbe Furious Freds a few weeks ago!]
Thanks for the tips and the nod from Exeter Man regarding the tyres. You're right I did have some Freds off you recently but those went to a friend so am looking for some more now unless I can work my beer persuasion again to get them back ! lol. I have some time this weekend so I'll see what turns up on Ebay etc and have exactly those grips and seatpost in my watch list already
although not heard of GUB and am a little wary of too cheap and too light perhaps ? Also I was wondering if some XT HT2 cranks would be better as have a spare BB for them kicking about but the M751 cranks only cost me a few beers so in the spirit of grams per £ will be hard to beat and am looking to put the money towards some good wheels as so far I'm safely under budget so could be stretch for something interesting. I have had some Crossmax SL in the past (and now have some SLRs on my Scalpel) and really like them but those tend to be closer to the £200 mark usually.