Thank you so much for your very helpful response.
I forgot to add that the bailiff letter was delivered by hand and open. Nobody was present at home and so it was found on its own through the letterbox.
When I say "I imagine" it's due to a court summons arriving in my absence, it is because I have some unread mail at my parents' from the last six months. The mail was not forwarded to me abroad as I have been in a remote area in a developing country and have moved to three addresses in four months whilst abroad. However, I managed to talk with my family on Skype this week and was shown the unopened letters in my name. Most look like bank statements but one is a thick envelope which could well be the summons. Should I ask them to open it? Does it make any difference if it is opened and checked with my authorisation at this point (bearing in mind it would be still be very late in the day)?
I still do not know for sure about the prosecution but, based on the original incident at the station, and now the bailiff letter, and the fact that I have not been involved in any other case since last July as I have been abroad, I think it is a fairly reasonable assumption to make. However, only the open bailiff letter has brought this to my attention as of last week.
I hope this clarifies the original points and that you will be able to advise me further.
Many thanks