Thanks. Re-running UMBR has fixed it and now I don't see any default menu before my menu.lst appears.
I checked glrdr in wordpad first and it did only show "configfile (hd0,1)/menu.lst" at the end (excuse the poor quality of this photo), so I don't know where grub/umbr was finding the default menu.
When I re-ran umbr I used the same command as before (I copied umbr to (hd0,1) this time to make it easier)
umbr -p=0 (hd0,1)/grldr
I might be misunderstanding umbr but does that tell it to look for grldr on (hd0,0) first and then if it can't find it there, on (hd0,1)? (hd0,0) is the recovery partition and didn't have grldr or menu.lst on it so I copied them across and it's a bit quicker now, the screen only flickers once instead of 2-3 times before the menu appears. Of course I've set grldr to load menu.lst from (hd0,1) but I doubt it would be any quicker if I changed it to load it from (hd0,0), so I think we've done as much as we can (and really it's fine anyway and my brother will never notice or care about any slight delay).