FAO: Stan Deezy
1. If its blue, has 2 pins and is a push fit into the coolant hose flange on the front of the block, then its famous blue sender, see part number earlier in this post :) If it has a screw thread, then I THINK its this one:
035 919 369 M - thermal switch, white, digifant - £25.19+VAT
2. 171 121 407 F - Square tank - £23.29+VAT
1H0 121 407 A - Round tank - £26.95+VAT
3. 443 121 321 - Square tank cap - £8.78+VAT
1H0 121 321 C - Round tank cap - £5.42+VAT
4. With a bit of fiddling yes, the brackets are different. The old bracket is spot welded to the suspension turret and the new bracket bolts on. The level sender plug is different also so you'll need to chop one off a later VW and solder it onto your loom.
5. If you mean hoses from GSF, mine have been fine for nearly a year now, cant see any degredation. From VW:
191 819 373 D - Return hose - £14.82+VAT
191 819 371 E - Feed hose - £16.80+VAT