The mash tun was also bought off ebay from the same trader who supplied the stock pots (cost approx £60).  This is a 24L insulated pot with tap.  I changed the original tap for a ½ inch Stainless Steel ball valve, the same as the ones on the HLT and Copper.  On a 5 gallon brew the mash tun drops around 1ºC over 90 minutes.

The mash tun false bottom is made from a 1mm Stainless steel plate with 1.2mm holes on 2.5mm centres.  The false bottom is support by 13 M4x40mm pan head bolts, with a stainless steel handle to allow it to be easily removed from the mash tun.  To take out any gap between the false bottom and the wall of the vessel I use some split plastic tubing around the circumference of the plate.

The bolts are just starting to make indents in the bottom of the mash tun, so I may need to change the design in the near future.