In all honesty I think just go for a decent brand when it comes to tyre gel and don't pay a fortune. There's a fine line when it comes to car care products. In my opinion things either work or they don't and if it works fine at £5 a bottle, why pay £50 a bottle?!
I bought some Turtle Wax stuff in a bright green bottle from Halfords a couple of days ago, used it and the tyres still look nice and black two days later. I work on a building site so that's not bad!