hello
depends on your time of travel, we stay in Argyll and frequently travel to France, leaving here around 4 or 5 pm, overnight at Westmorland Services at Tebay as they have a site then onto Dover next day - give easy run, however we have an extra 2 or 3 hours longer travel than you - in the past we have also used the Royal Umpire site near Leyland in Lancashire as it has pub with food just outside but you need ta arrive before 5 and leave after 9 the next day but give relaxing start.
You should be able to do Glasgow to Folkestone in around 10 hours or so, allowing for breaks and traffic