He might be busy with relatives for the holidays, don't read anything into this. Just relax. Text him when you get back to Leeds. It's not being clingy, it's good communication and showing an interest. If you don't show an interest you will lose him for sure.
And stop waiting for him to do all the work. You should ask him out when you both are back into a routine after xmas. And if you ask him out, don't do it via text. Texting might be fun and "high tech" but it's really low class to ask out a date via text/SMS. Don't be a chav.
I have a long time interest in psychology, specializing in relationship dynamics for 30 years.
(Please note, we give the best advice we can based on the information given in a post. For better advice, please include the age of all romantic partners.)