The UK has for many years only been cutting the Top Right corner off of the Front & Back hard cover pages and the personal information pages. They normally leave all the other pages intact if that information helps.
I have a SETV Non Immigrant and Immigration told me I was OK for a 30 day extension but I went too early last time and had to wait nearer the expiry date.
I have sent her a letter of invite from me, an official letter from the St Patrick's Society inviting her to the Ball, photocopies of my Thai apartment complex where she will be staying, a photocopy of my UK Passport and Thai Driving Licences. I have said in my letter of invite that I was covering all her costs but I hadn't intended to send her money to the Philippines as she would get it in Pesos and would need to change it again when she got here. Seems like a waste to me but if she needs cash in hand then perhaps I had better.
This is the list recommended by the Thai Embassy in the UK but I understand that it is only a recommendation and not binding. I tried them all but only one would do over 70's and then only until 75 (at very high cost)