Our flight came in at 23:35 and by the time we got to immigration it was already after midnight so we were stamped in for the next day. If you have a round trip ticket I don’t believe you will have a problem. I once did the same as you and was told not to worry it happens all the time. It’s not like you are staying 10 or 20 days over, it was a simple error and the Thais understand. It will cost 500 baht per day. Relax and enjoy 😊
That’s what you want and the Thais want you to enjoy as well.
If you are from the US I think you get 30 days on your passport and then can extend for 30 days; however, I don’t know if that is the same for UK citizens???
My grandson was having trouble getting his passport, it was taking forever. I told him to contact his representative’s office in Congress and let them know the problems he was having. Thankfully his reps office got involved and he had his passport a couple weeks later. They are super slow…..