I am surprised the police didn’t take both bikes away until it is resolved to their satisfaction. That’s why you should have class 1 on a big bike and let the insurance company do the talking.
I am not sure the British embassy issues the letter anymore. Immigrations issue is how the money arrived in your U.K. bank. You need to prove it is legitimate. My issue was a catch 22. I could show the money in my U.K. bank. But I have no wages as I am retired. I am on a retirement visa remember? An old P60 was not good enough to prove it is savings from a legitimate salary. They would not budge and don’t care either. I switched to the 800k method now.
I had a similar issue. I had one years bank statements. Receipts from Wise showing International Transfer to reconcile the bank statements. All no good. They want an embassy or pension letter to disprove AML. This is Thailand.