Ok its been a while but I've now had the Sprocket cover off Pulled the Shift shaft seals out & cleaned up the recesses, tried the bearings to see if they were actually going to fit or not.
They fitted a treat, nice & snug as they needed tapping in, so cant see them coming out unless there tapped put.
What a difference they've made, No more shaft play at all & shiftling gear now feels so much better.
I so wish I'd done this sooner
The bearings used were bought from Ebay (seller - Leomaxx22)
Advertised as "2pc 12x18x4 Rubber Sealed Ball Bearing Tamiya Kyosho Traxxas"
They only cost £2.13 so even if they only last a year they ain't going to break the bank