As many folk will be collecting all the parts together before they start, Brian has prepared a list of bolts etc. that one might choose. One can, of course, use many of the cheesehead screws supplied with the Roundhouse kits if preferred.
In the UK, small head BA bolts (though not all sizes listed above) are available from:
www.ekpsupplies.com (thanks for that Ken Povey!)
And please let me know if there are other suppliers that I can list here