I recall PEN 1S (or was it PEN 15S) was on a 7.5 tonne (?) parcels-type lorry in the Bristol area back in the 70s. Orange in colour IIRC.
I recently purchased a personalised registration, and including fees, number plates and everything else, the cost was only just over £300. It looks like a "standard" issue, so nothing to get too excited about, just that I know it's mine!