You can apply for a 90 day Non-O visa based on marriage to a thai using the online eVisa portal thru the thai consulate in London before you leave.
you show proof of funds in the UK to get that visa issued you don't need to bank it in thailand to get the visa before you come here
Once you're here you need to get the 400K baht transferred into a thai bank account in your name only as soon as you can because it needs to be in the account for 2 months before you apply for the yearly "extension of stay" based on marriage at the immigration office where you will stay in thailand.
The visa you get thru the London consulate will be valid for 3 months from the date it's issued, <- that means you have that long to ENTER thailand and when you do you'll get stamped in for 90 days.
You can apply for the yearly extension at most immigration offices when you have 30 days or less left on that 90 day entry stamp from the Non-O visa
This is the link you apply at
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and this is the choice you want on that system