The link below will somewhat clarify the situation regarding customs duty and VAT due if you import my cameras into Great Britain (does not apply to N.I which remains in the EU customs union).
As such it appears that any order up to a value of £135 (so any order of 6×6, 6x6f or 6x9f camera) would not incur customs duty though VAT would be payable upon delivery by the customer.
Orders above £135 ( e.g 6x12s and 6x17s) would incur both customers duty and VAT.
Correctly filled in customs declaration form CN23 will be included with any shipment to GB.
Hope this helps to clarify the situation!