[Blind Mapmaker]

Merchant Guilds were established fairly early in southern England and they remained strong for a long time. I can't say whether they introduced letters of credit in the 13th century, but it doesn't seem to be much of a stretch. Shropshire is a bit out of the way, but the wool trade would make it important enough.

The other two options for forwarding money are church organisations (the Templars have been mentioned, but members of other orders or priests of a diocese could be entrusted with money) or distant relatives. Kinship networks were fairly strong on the Celtic fringe and people would probably think twice about embezzling money intended for "grand cousin Oswald's godson who's learning magicks in Womel".