Had it booked into Agnew Autoexchange Seat today and they've sent off a warranty claim to Seat to hopefully get it replaced, didn't charge me at all contrary to what the fella said on the phone, just awaiting them to call me back to deliver the verdict.
Would the odds be high for Seat to approve to replace it? Would Seat know that I've had it looked at previously and that it was also a previously rejected warranty claim?
So Agnew Autoexchange got back to me and said the warranty company turned down replacing it, seems it's not up to the dealers to replace the light or not, maybe it's because mine is a Seat Extended Warranty for used cars rather than the 3 year new car warranty.
I've tried the 2 nearest dealers to me, one about 25 minutes away from me, another 50 minutes from me, the next would be an hour away, don't think it'll be worth it making the trip down as I'll probably be met with the same outcome, think I'll just buy and fit one myself.
I've attached a few pictures of what the crack and subsequent condensation looks like on my rear right tail light.