Thank you Loiseau, Hectorsdad and others for your comments / observations re the sale of my property.
Regarding transfer of funds - which may be quite a lot - it’s worth opening an account with more than one currency firm so that you can get get the rate of exchange for your transaction(s) from more than one firm, compare them and select the best deal. It’s also worth talking to a dealer as you can negotiate the best deal rather than purchasing sterling online. In my own case I did several deals, almost always used the same firm as they consistently offered the better rate of exchange.
To illustrate this point, an anecdote. Years ago, when wanting to buy sterling with US dollars, Moneycorp (UK office) were able to give me a rate which was about £12000 better than a US bank would give me for buying sterling.
Moral: specialist currency firms tend to give better rates than banks.
Several comments here about a “barrel” being a property. What is a “barrel”? I know the French term “barrak” which tends to be a slang term for house / dwelling, may even be pejorative.