I generally agree, there’s always someone willing to "help you" for 25-35K baht with something at an actual cost of 1900 baht. I would never use agent myself either.
But, a border bounce cost between 3-4K baht including everything and it guarantees you an additional visa exemption. I think that’s a reasonable price for something you in fact sometimes can’t do on your own.
If you hold a passport from GB or Ireland you don’t need a visa for 90 days as Stepehen explains. Just get a cheap ticket out within the initial 60 days if you’re airline ask for it.
Only two months counted in days, so 62 days is fine. You don’t necessarily need two full calendar months. The 19th one month until 18th next month gives one month.
You could apply for a 90 days Non O based on marriage through the Thai embassy in London before you go, put 400K baht in a Thai bank account two months before you apply for yearly extensions of stays. If you also purchase a multiple re-entry permit you’ll be able to come and go more or less as you like.
Alternatively a Non O based on retirement and bank 800K baht for the first year extension of stay and switch to monthly income for the second year by showing proof of twelve months consecutive transfers of min 65K baht.