When I went out to the shed this morning I found out what the two clips do, they hold the grown-wheel and planet gears in, as I had a drain bucket full of parts
next move was to remove the tranny (didn't have room to tip the tractor upside down) and after a lot of head scratching I got all the parts back in and refitted the sump.
on moving the axle back under the tractor the nearside driveshaft slid out so stripped it down again and one of the locking clips wasn't rite in.
now its back in the tractor, just have to fill it with oil and see if it works