Advice on problem with tax advisor in England

I would appreciate some advice about how to proceed with this please.

I am dual Spanish/ British citizen, resident in the UK for over 20 years.

I sold some property in Spain which came from an inheritance, and as required paid Spanish tax at the time.

I then engaged the services of a UK tax advisor based in England, for them to submit the UK tax self assessment for that year in relation to the sale.

I signed a contract with his firm in August 2023. At the time he stated it could be finalised by September 23. He informed me the deadline was end of January 24.

Unfortunately, after multiple emails, he stated that he had submitted my tax return to HMRC, I believe in paper form, sometime in November 2023.

I kept chasing him up to confirm submission, and by February 2024 he said that he had contacted HMRC and didn't have authorisation, but believed it had been submitted correctly.

I then received a fine from HMRC due to my tax return not being submitted on time, and now realise it was never submitted at all.

My last communication with him was in February 2024, then he sent a bill for his fees.

By that point I had lost all trust in him, and I engaged a different tax advisor who confirmed the tax return hadn't been submitted, and who did the submission without any issues.

I was angry at the time, and didn't make a complaint about the first tax adviser, I buried my head in the sand and never paid his fees.

He has now, in January 25, sent a reminder of unpaid fees.

My question is, if I wish to make a complaint about the tax advisor and not pay the fees, as he never fulfilled his obligation towards me, what steps should I follow, please?

Should I make a complaint to his firm first, or is there an advisory body I can contact first?

The other thing to say is that he signs his emails with 'Tax practitioner', so I am unsure about his qualifications.

Thanks all