As others have said, insurers are categorically not allowed to offer a smaller sum in cash than they would in vouchers. The insurance ombudsman has explicitly criticised insurers for paying out in tied vouchers rather than cheques a few years ago, though they still do it, as presumably most people just go along with it.
[1] The Financial Services Ombudsman has ruled that:
“The option to replace jewellery is not properly exercised by offering a policyholder an authority to buy jewellery up to an agreed value at a particular jeweller’s shop. That is wrong in principle, although it seems to have become a hallowed practice. It is, in fact, a denial of true indemnity.”
[2] If you cite this and therefore ask for a cheque rather than vouchers insurers will generally try to reduce the payout. At this point you should cite the FOS's website @
http://www.financial-ombudsman.org.u...place-cash.htm
- "Policyholders should be allowed to choose where they purchase a replacement and they are entitled to a cash settlement if they cannot find an acceptable alternative. In such circumstances,
we would not regard it as reasonable for the insurer to make a deduction from the cash settlement to represent any discount it would have got if the policyholder had bought a replacement from one of the insurer's nominated suppliers."
[3] There follow a list of recent cases where the FOS has duly upheld customer's rights to have cash settlements.
So, insurers are emphatically [A] not allowed to insist that you take store vouchers instead of cash, and [2] not allowed to offer you less in cash than they offer in store vouchers.