Hey mate
I have no idea on price but id also like to know, Im from Middlesbro too and i have (Kinda) the same bother,
I have a blockage under my scuttle panel causing a leak into the car, (which i know you dont have.)
But im worried about taking my scuttle panel off to clean underneath incase i crack mine or snap those pins that hold it on, as im not sure if they pop out or screw, but my moneys on them popping out...
I dont think mine is quite as brittle as yours sounds ( i hope)
Let me know if you get a dealer price, a second hand one might not be in much better shape!
If all fails i can tell you there is a good breaker called s.p.c morgan in guisborough which will likely have one if you pay them a visit
http://www.morgan-autosalvage.co.uk/Their website parts list isnt always up to date though so its always best making a call or maybe going down to check
