They better be good for that kind of money.
I'm pretty sure that's the most expensive t5 bulb I have ever seen (I haven't been looking for very long, only use my T5 for prop/early veg).
And I mean, it'd be expensive if it were 25 USD, none the less GBP. God damn I hope that's at least 4 pack.
EDIT: You'd probably be better off mixing them up like BigV (I meant Illegal Smile) mentioned, and buying seperate 6500k & 2700k bulbs. That's my 2 cents (keeping in mind I have no idea what I'm talking about, just saying stuff hoping people will set me straight, lol). Either way, It'd probably be cheaper buying seperate 6500k and 2700k bulbs, compared to that dual spectrum deal.