In which case, take screenshots of his website as proof of what he stated his qualifications are. This is important for any court claim as it will form part of your evidence. Do you have his address? If so, write to him (and obtain proof of postage at a post office) giving him X number of days to make contact and arrange to look at the floor with a view to assessing what is required to put right the issues. Otherwise email him or text him. Screenshot any messages.
Don't send a letter which needs to be signed for because he'll probably ignore any 'while you were out card'.
He'll either respond or ignore you. If he ignores you, get someone round to quote for putting things right. Get the quote in writing.
You can then decide whether to send him a letter before action, i.e. before making a small claim against him. Ultimately you can obtain a CCJ against him or his company if he doesn't pay you back. Alternatively you could issue a statutory demand for your costs in putting things right. If he doesn't pay a stat demand for a minimum of £750, you can apply to get him made bankrupt or have his company wound up.
Whether you will get your money back is another thing, but you can get a CCJ against him or his company. It's important if he was a sole trader you address everything to him personally. If he is operating via a limited company then you address it to the company.
Whatever you do, stay calm and matter of fact. Don't make any threats or repeatedly contact him, just make it clear what you want him to do and provide reasonable timescales.
We have just had an LVT floor laid. It was ply boarded and screeded to level on one day and the flooring laid another day. You can walk on it straight away. We were advised to leave it overnight before moving a couple of heavy appliances back into place over it, but that was all.