Your biggest problem is for your wife to provide the evidence that she's going to come back to Thailand ie she has a job and money in Thailand and maybe a family members to come back to or a home that she owns
If she does not have any of them then she will not be coming to England, no matter how much money you have in your account
For me Bangkok Bank is the best for your problem so if I was you I would change my bank account if possible or do you have any friends who are with Bangkok bank as they will have a letter from the bank to help you to show it to your bank