So after a little advise I looked at the KLM option via Amsterdam and like you say "getonittt" they do actually come out far cheaper at just £228.50 compared to Monarch’s £391.94
Also whilst looking around checked out the British Airways option via Heathrow it too came out cheaper than Monarch at £315.08
If that's the case why do Monarch charge more than a national carrier? is it for the privilige of flying direct non stop? I know 2 friends found flying from BHX to BCN was cheaper flying with KLM.