Hello, I'm Keith and happy to help you with your question.
Here is the Gov UK advice premable on the subject of the UK Flat Rate VAT Scheme:
'To join the scheme your VAT turnover must be less than £150,000 (excluding VAT) and you must apply to HMRC'
From which I deduce from your question that with your turnover you are outside the scope of the Tfat Rate Scheme and must operate normal VAT procedures.
I am so sorry to have to rain on your parade.