Recorded delivery - car insurance claim

I had a minor bump in my car last week. A driver went into the back of me and admitted fault. Only minor damage to be resolved. I was in no way at fault.

I rang my insurance company and he did to his admitting fault to them.

I set the ball in motion to get my car fixed through my insurance company as my preferred option. I then received a call from the third parties insurance saying I should get the repair through them giving me all sorts of scare stories about a rocketing premium if I go through my insurance for them to recover from them. Also they offered me £100 to go through them. I said I wanted to think about it but it did sound interesting.

In the meantime they sent me an email saying thank you for agreeing to get my car repaired through them as their driver was at fault. I never agreed to this only saying I liked the sound of it but wanted to check with my insurance.

When I got this email I rang the third party insurance to explain and say I did not want to use them within half an hour of them sending the email. They said that was fine and said they would await details from my insurance.

I spoke to my company who agreed they would carry on with the repairs.

I still then got a call from the third parties repair garage to book my car in! Email the third parties insurance to confirm I do not want to use them.

I then returned home to a card from the postman for recorded delivery letters which I need to sign for. I'm really worried about what these could be an I am now away for a week. I'm not expecting any recorded delivery letters and I'm worried they could be bin relation to the confusion about who is doing the repairs.

What is normal in terms of recorded delivery letters in a not at fault claim. I'm worried the third party insurance might be trying to recover costs or something due to this confusion.