Does anyone know the gearbox code on a 1.4 MPI 8 valve it's a y reg

Look at the specification sticker in your boot. Probably stuck to the metalwork near the spare wheel.

Had a look there and I have a code which is etd is there any other gearbox compatible with this code

Go to the gear ratio FAQ and download the two PDFs in there. You'll find your one near the end of the second one. You'll see all the ratios yours has, compare those with the ratios of the others and you'll see which ones are the most similar. Preference also comes into it, if you'd like longer gearing for cruising and economy then note those units, or closer ratios, or shorter gearing, depends what roads you use and how you like to drive. Your current ratios were selected to be a good all rounder or compromise for that engine, weight, spec of Polo.

I had a recon box recently and i dont know what cc polo it was from but on my 1ltr at 70mph it was at 4000rpm and with the new box it was at just under 3000rpm at the same speed.I'm not complaining though it does like a 60 mpg now . : )