Euro car parts do an oil filter service kit for your gearbox if it helps, I think about 170+vat last time I purchased one but includes the oil, new plastic sump with bolts, filter, correct meyle oil and a few rubber bungs needed. Much cheaper than buying all Seperate from the dealer.
If it's your gearbox then you're gonna be looking 800-1200 to recon plus labour and new oil.