BC should work across the store according to BC…
Members and official Fans of British Cycling can get 10% off everything in-store at Halfords, including sale items.
List of T&Cs from BC site:
Discount is supplied to British Cycling members with a valid British Cycling Membership card.
10% off is valid on any purchase, excludes gift vouchers and Halfords Autocentres.
May not be used in conjunction with any other voucher.
Discount can be used in conjunction with other instore promotion unless clearly stated otherwise.
Discount can only be used once per transaction.
Discount is not redeemable for cash.
Exclusive to British Cycling Members.
Discount is not redeemable online.
It does also say
Excludes all website only prices and deals
but I think thats just because you can’t use the discount online?
I’ve never had an issue getting the discount on click and collect, or having them price match their website or others and then apply the discount.