Hi Jason
As I don't know what the old price is I can't really comment.
The renewal price would probably depend on how long you had the subscription.
The gift is free when compared to the current subscription price.
I think this is very fair.
Check the subscriptiopn price in the last magazine with the offer price with the free gift and the only difference is the £5 post and packing.
I doubt you will be paying more than £5 above your renewal price so you will be £25 gift minus £5 additional subscription charge = £20 in hand,
regards david