Most of the timber has come from "normal" DIY suppliers. This needs to be sourced locally, because of the bulk. Make sure it is straight: much of the timber available - even supposed constructional stuff - is warped and some would be good for building around corners. Store it flat, and preferably in the railway room for a few weeks before starting work.
Joints are glued and either screwed or nailed. Don't skimp here: it needs to stay solid through its life. Most of the screws were from Screwfix, as were the brad nails where used. PVA wood glue is readily available from DIY merchants in gallon containers, and it is much more cost effective in that quantity.
I used adjustable "feet" under all the legs. as constructed, the railway would be robust and stand flat outside the shed; it is attached to the wall at the very end to prevent accidents more than anything else. The feet, and the threaded inserts into which they screw were obtained from Ross Handling Limited for approximately 50 pence per leg. Leg part number 38SG-100; the matching threaded insert part number 250817.
The trackbed is 1/8" cork sheet, obtained from Quality Cork Supplies in Wednesbury (0121 567 3140). They advertise in Railway Modeller.