UK Postcodes - Trim to just the 1 or 2 letters

Our main use of Monday is sales leads.

When leads come in they have a UK postal code assigned, whoever deals with the area of the postal code is assigned the lead. We take the first letter or 2 and use a vlookup on another Excel sheet to decide the assignee

Currently this is manual however I would like to automate this. Excel allows me to pull the letters from the postcode using either of these formulae (assume the postcode is in cell C2);

  1. =LEFT(C2,2—(ISNUMBER(VALUE(MID(C2,2,1)))))
  2. =IF(ISNUMBER(VALUE(MID(C2,2,1))),LEFT(C2,1),LEFT(C2,2))

If I can replicate these formulae in Monday, automations can do the rest however I can’t replicate these successfully. I can’t use LEFT({postcode}, 2) as some UK postcodes start with only 1 letter therefore doing this would return a letter + number.

Any suggestions/alternatives would be greatly appreciated.