Yes , this is completely normal with hotels
If what the OP is describing is an actual transaction for £150 followed by a refund of £150 (ie, it will appear on the statement as two items, cancelling each other out) then it's actually nothing like normal: I stay in about twenty hotels a year, and I see it perhaps once every few years and get very cross.
It's extremely anti-social, because it exposes the client to foreign exchange risk and, in almost all cases, to the bid/offer spread on foreign currency on a credit card, as well as any commission payable.
The hotel should take a pre-reservation, and then release it on checkout. Unless you are in the unfortunate position of travelling with a credit card which doesn't have a lot of headroom, that's invisible to the client, and free to the client. If they make a transaction and then refund it, that costs them money and, in many cases where the currencies aren't the same, costs the client money as well.