Hi Elaine
have to say ive enjoyed reading all the comments and advise uve been given regarding ur dilemma, ultimately it is up to you to decide if your fit enough or not to do the course, all have given very valid information, if you feel that you have a good base fitness then work at it over the next week and put in some test runs to see how you perform.
I know considering its going to be your first that you would like to get a good time in, but it is sometimes better just to complete on your first one and that way it allows you to see where the land lies for future ventures. I have a course that I posted on
www.mapmyrun.com "toon route1" try that out in one on a training run this week and try and do round the moss road for your long run on sunday, if you can manage to complete both of them by next week and feel ok at the end of them, then ull manage to complete glasgow in 4 weeks time if you can keep running at these distances, really you dont need to train beyond 10 miles for a half, your fitness will carry you on beyond that and the crowd and the atmosphere are worth a couple of miles to you.
The "toon route 1" is probably the toughest urban run ull get around campbeltown and its a lot tougher than anything ull experience in glasgow, if you cant do a full set of 10 on Mcleod homes brae then at least try a few and go right up and around on your last one, there are only 2 climbs in glasgow worth bothering about , at the start and up paisley road west towards bellahouston park