[Colour Temperature]

sounds like the bulb then. Unless you can get a bulb from the same place you bought the kit I would suggest changing them both to ensure the same colour

[Colour Temperature]

The bulb determines the colour but it could be either thats causing the problem. If the bulb is dying then you would get that effect same as if the ballast was malfunctioning it can't ignite the bulb properly

[Last resort - ask on here! Haha]

did you try PD Tuning in Boldon?

[import tax]

they could mark it as "Gift" but the declared value can't be anymore than £40 or you will incur import VAT, over £135 and it will be import VAT and Customs Duty

[Spring compressors...]

he's sold 655 sets and I can't see any negatives for them

[Underbody lighting - Yes or No?]

As with any thing you do to your car other peoples opinions shouldn't count. If your relying on other peoples opinions to make your decision then in my eyes you shouldn't do it because if you really wanted to do it you wouldn't need opinions.

You do something to your car because you like/want to not because others think it looks good

(meant in the nicest possible way)

[Underbody lighting - Yes or No?]

This what the ones look like that I put on our car. They are not on a switch as such but controlled via a remote. They can be whatever colour you want them to be, the remote has preset colours and patterns but also has 3 DIY buttons for making your own colours. They only ever come on at shows and unless they are turned on you would never no they where there

[Xenon blue bulbs]

You won't get much useable light from them and it wouldn't suprise me if you get pulled over by the old bill on more than a few occasions.

[100w bulb set.]

I was just wondering if these would be suitable in my car (gen 6). I know it clearly says Celica GT 93 - 99 but I read in a thread somewhere that they can damage something, don't remember what it said exactly lol.

Yup, other road users eyes. It does say in capitals that they are not road legal.