Looks like a decent price. Not in stock currently, but they'll deliver when they are.....so as long as your teeth won't go yellow in the meantime!
According to the Philips website (link below), these are compatible with the following brushes:
2 Series plaque control
If you want/need to stock up - order 4 packs to take the total to £40.40, pay by Mastercard and enter the code 'Priceles5' to get £5 off, taking the total to £35.40.