You keep going on about “witnesses” Eddie. This gentleman is clearly not a witness but with garbled snippets of confusing information it is impossible to say what has happened. However my money is on the fact that he has almost certainly been told to attend court under the Postal Requisition system as explained by Zacs-Master at 21:30.
Witnesses do not routinely receive summonses. Except occasionally in cases such as matters of domestic violence, where it is suspected a victim witness will not attend unless summonsed, witnesses are normally simply asked to attend court. Otherwise only if they fail to attend when asked is the question of a summons raised and it must be raised with the court. Police have no powers to issue witness summonses and they must be issued by a court, even in the domestic violence situation I mentioned above.
But as suggested, a solicitor is the best bet to establish what is happening for sure.