I bought a tin of H&N FTT's Tone, quite a tight fit but nothing that leaves a 1/4" circle on my thumb.
Looks like I will have the job of taking the Mother-in-law to Kings Cross Station to catch the 12:19 back to Sunderland on Saturday so that's my Range time banjaxed. Maybe take it over to my permission on Sunday and get it zeroed up (on a few rats hopefully)