You would have been given a document when you were stopped with details of how to appeal.
As the letter says, you were then issued with a reminder notice via post on 03/11. It appears you ignored this.
You then received the letter dated 20/11 with a final chance to pay to avoid prosecution - having missed the deadline to appeal, they were correct that you had to pay to avoid criminal proceedings.
Presumably (as you seem to have received everything else) you got the letter advising you that the matter was going to court, and you ignored this?
You then ignored the Further Steps letter from the court notifying you of your conviction and seeking payment for the court fine, so it has progressed to debt collection.
You ignored the first letter from the debt collection agency and they have now moved on to seeking to remove your possessions to pay the outstanding debt.
I don't think there's any way out of this without paying the fees demanded now or engaging with the court. It's rare we see cases that have progressed so far, when the OP seems to have received all the paperwork as it proceeded....