@Jenny1342
I have no knowledge about tenancy rights in UK, so maybe another (local) host can respond on that.
But.... when you use the "change" option to extend a "short term stay" into a "long term stay", be aware of glitches in the change form, especially regarding the calculated price. Always also manually calculate the price and if neccessary amend the price in the pricefield. Most common issue is: the stay has a weekly discount (if set), but by extending it the monthly discount (if set) will apply, also retroactive.