Couple more (small) pic updates.
Sourced some screws to lift the washing machine drum off the UDS floor (for the ash to escape into).
Best screws for the job where M6 x 90mm stainless steel. They don't really need to be any larger (the wash drum isn't that heavy) and the M6 size is a bit cheaper than the larger sizes (contemplated M10 at one stage).
Fortunately there were three holes at the bottom of the drum (would've been connected to another part in the washing machine) which were a perfect fit for those screws. Three is enough to balance the drum from the ground.
90mm size gives me enough room to secure the bolts with nuts either size of the holes in the drum (washers not required due to the holes already having them built in) and still having approx 3" height from the ground. You can adjust the tightness of the nuts/bolts so the drum is level (just count the threads at the top of the bolt).
As I mentioned above, I may add an ash catcher into the mix (using the same bolts but securing them through holes drilled into the metal pan). Not a real necessity however: yetidave - do you just hoist the drum upside down to get rid of the ash at the bottom periodically?
Also on the look out for handles (and possible a couple of wheels, but these are add on items I'll add as and when. The availability of those metal/wooden BBQ handles is pretty low.
Pics:
These are the bolts (£2-£3 from screwfix):

The hole saw and arbour (used with a SDS but probably not necessary) - these pair were absolute workhorses - probably drilled 50 odd holes (oil drum and washing machine drum) before it gave up the ghost (actually, just the drill bit snapped - possibly more life left in that hole saw). These were from tool station.

M6 x 90mm bolts secured to the wash drum:

Washing machine drum on the bolts/legs:
