Go with stainless steel, Ti are great for saving the last final gram but not really necessary and can break if over-torqued. After you've tightened the bolts, pop a small amount of grease on the allen key and get it inside the bolt head, it'll stop it rusting.
Note that some stems use a fractionally smaller head diameter than is the standard size and using the larger size may not fit correctly and put extra strain on the area around the bolt head on the stem. Don't have a comprehensive list of stems but just measure before you buy. Of course the head can always be machined down somehow but a lot of effort for such an inexpensive part. Here is one place that sells the smaller head bolts and unfortunately only in Ti and in Canada but not too expensive. http://www.torontocycles.com/Selling/Ti ... Bolts.html Look near the bottom left of the page for "Ti Narrow Head Bolts" Possibly somewhere in the UK stocks something similar as well.
Posts
http://www.sjscycles.co.uk/nuts-and-bolts-dept373_pg1
i live close to the sea in a hot humid city. Ti bolts seemed like the way to go.
2007 Cannondale F700 CAAD
2010 Cube Agree SL (Road, retired)
2011 Cube Litening Super HPC DI2 Frame, with Ultegra Di2 Components
http://www.screwfix.com/p/socket-cap-sc ... f-50/14216
Specialized Secteur
How's life in Sunderland taimur? I miss the north east