hey there, strange for this to happen, is there any sign of water getting in ?
the bulbs at £35 are unbranded right ? not the phillips ones which are about £60 each,
it is common to get a difference in colour when only replacing one bulb as with anything not getting them from the same batch number let alone a different manufacture will be different.
if the same light has went through 2 bulbs in a very short time then eithe you have been unlucky with the bulbs or the power pack if faulty.
have you tried the bulbs in the other headlight just incase they are still working, if they were then it would show that it was indeed the powerpack.
i had a customer who had a simalir situation and it ended up being water in the powerpack due to the headlight leaking
any questions just fire away
Paul