Correction-got my suppliers mixed up; Metall Nord are good for cheap Aluminium (unless you have an Aalco account) bought my 7075 from them.
Titanium we've bought from TiTek
http://www.titek.co.uk/
Tel 0121 382 4121
Fax:0121 373 0489

Not the cheapest but they can get you what you want.