you dont have to visit the embassy you can do it by registered post. If yo do visit in person it is a two trip job one day fordrop off next for pick up.
if you plan on staying 70 days you MUST get a SETV visa. This gives you 60 days extendable for another 30 days for 1900 baht at immigration. Otherwise you can only get 30 days visa exempt extendable for 30 days etc etc. Easy to get look at your nearest Thai embassy.
Gettng a SETV from the Thai Embassy in the UK is easy send your fee a SAE passport 2 photos and a completed form. You dont need to show funds or even a ticket
Could be as Noel is suggesting no return ticket could be they haven't cleared him from the system. The airline would of told him. Actually come to think of it in Scotland dont they check at the airport you have paid any court fines TV licenses and similar before you are allowed to leave.