Diminishing musharakah
You and the bank buy the house together. You live in it and pay rent on the bank’s share. Each month you also buy a slice of that share. Over 25 years the bank’s share falls to zero. That is a partnership plus a lease plus a series of sales — three contracts, not a loan with a smile.
For this to be real, the bank must own its share (registered, or beneficially in a way English land law accepts), rent must relate to usage of that share, and extra units must be sold at a disclosed price. If “rent” is just interest on outstanding principal and you never actually co-own, the label is decoration.
Ijara and murabaha
Ijara: the bank buys the house and leases it to you, with a promise to transfer at the end. You are a tenant until then. Repairs and insurance should follow lease rules, not sneak loan terms back in.
Murabaha: the bank buys the house and sells it to you at a disclosed markup, payable later. Fine for a fixed-price sale. Awkward for a 25-year home with rate resets — which is why UK retail home finance rarely uses pure murabaha for the whole term.
UK frictions you will actually hit
Stamp Duty Land Tax, Help to Buy, and most lender panels were built for mortgages. Home Purchase Plans are recognised by HMRC so you are not double-taxed on the bank’s share in a properly structured product — still, instruct a solicitor who has done one before.
Islamic home finance in Britain often prices above a comparable SVR. That is not proof it is fake, and it is not proof you should take the cheaper conventional mortgage. It is the cost of a smaller book, extra legal work, and not using LIBOR-era interest. Run the comparison tool; then read the late-payment clause. If a missed payment grows the amount owed as interest would, walk.