I note that the payment section on the SET(M) application form page lists:
If you are applying by post or in person, you can choose how to pay your application fee:
by cheque in sterling on a UK bank account - the application form will tell you who to make the cheque payable to, you should write your full name and date of birth on the back, and attach the cheque to the front of the completed application form;
with a UK postal order - you should write your full name and date of birth on the back, and attach the postal order to the front of the completed application form;
with a credit or debit card including MasterCard, Visa (including Electron), Delta, and Maestro (including Solo). We can accept any Maestro card if you are applying in a person at a public enquiry office, but only Maestro cards issued in the UK if you are applying by post. You must include the card number, the amount paid, the payer's name as it appears on the card, the 'valid from' and expiry dates, the card verification value (CVV) code, the cardholder's signature and the date. The issue number is also needed for and Maestro cards. If you are applying in person at a public enquiry office, the cardholder must be present in order for the payment to be taken.
Payment by any other method, by post or at a public enquiry office, is not accepted.
That would be unfortunate - I used a banker's draft for my FLR 2 years ago, and it was certainly the easiest, quickest method. No waiting for cheques to clear, no sending account details through the post. I know I can use a postal order to avoid these issues, but as far as I've gathered you can only get those in denominations up to £250, which suggests to me (incorrectly?) that I would have to get 4 individual postal orders totalling the £900 fee. Given that you have to pay for each postal order, I'll probably just send a cheque and accept the extra week of processing time.
ETA: Hmm, although I find that the SET(M) form itself says:
You must pay by one of the methods specified below.
• Cheque
• Postal Order
• Credit card1 - Visa (including Electron), MasterCard
or American Express (Amex)
• Debit card - Delta, Maestro* (including Solo)
• Banker’s draft (payable to the Home Office)