It doesn't matter if you pay £100 or £1000 your lady will have to provide proof that she is coming back to Thailand after the holiday when she is at the interview in the embassy
0 in a separate bank account for the immigration and just forget about it and use it every year to show them. Make sure that your account is easily accessible to keep the immigration happy
I did it myself without any problems, your right about the house and kids but they have to believe what she has to say about her life in Thailand and that she will be coming back to Thailand
You can do it yourself, she'll need a job and money in the bank a letter from her boss will help you also you will need to confirm that you have offered to take responsibility for her in England. It will also help her you have money to support her in England in the bank and you have housing for her to stay