You can't get Non Imm OA visas in Thailand, however you can apply for Non Imm O visas but you will each need 800k Thai Baht in Thai bank accounts and proof the money was transferred from abroad.
Yes of course but only if you own the property, as I quite clearly stated in my reply. I mean which bit of "unless you own the property" didn't you understand?
You're most likely to have problems boarding your flight from the UK on a one way ticket without a long term visa or proof of onward travel within your stay in Thailand