I never said it was…. I’d suggest re-reading my post
It’s a re-mortgage the poster was asking about, there are no other parties to engage with.
The lender will normally appoint a solicitor and pay for it to deal with the legal elements of the remortgage (you can appoint your own if you want but you’ll have to pay for that).
If your transacting, it’s the solicitors job to update the relevant parties, you don’t need a broker to do that and normally your own solicitor will also act for the lender if they meet their criteria. There is no absolute requirement to use a broker but as I said in my post, if you are not a straight forward customer, you may be better off with a broker to do the legwork for you.