Naturalisation is applying for citizenship if you live abroad I understand. It's the legal process to obtain citizenship if you don't have a permanent address in the UK. I believe that's the difference. My Thai wife is a British citizen but she had to have lived in the UK for three years under leave to remain visa and have a permanent address in the UK.
They all have different rules. Even the same company can have branches that have different rules. Keep looking at watch for any recommendations on here from those that have been successful. I opened one 8 years ago in a 30 day exempt
When I went a few weeks ago they were dealing with hundreds of people from Myanmar under this new amnesty. They may just be busy. Our office is normally so quite
I had the same experience. As soon as you are no longer a member they change. I even out of desperation tried to sign up again and they said I had to leave the country first to clear my overstay. I told them I have never been on overstay I went into amnesty though no fault of my own. They just wouldn't have it.