You are quite right. Utrecht has a more particle physics-based curriculum, which is good, if that's your thing. But at the same time, you pointed out Quantum gravity as one of your interests. You need solid General relativity for that. If I were you, I would prefer Glasgow. (t'Hooft himself is more of a particle physicist).
You can check out Glasgow's curriculum for MSc in theoretical physics here-
http://www.gla.ac.uk/postgraduate/taught/theoreticalphysics/
It was not really a part of the question (:P) but nevertheless, I cannot help suggesting Perimeter Institute. It is affiliated to university of Waterloo(but it is quite autonomous), and has THE best postgraduate course (PSI) I've heard of (http://www.perimeterinstitute.ca/training/perimeter-scholars-international/psi-courses). The faculty members are top class. Check out their website. They have sorted out the faculty according to their fields of research. And since this institute is only meant for theoretical physics, you will get no-nonsense course. So, check it out.
And mate, since you are going to get a Masters, can you suggest me what should I choose for my undergraduate? I am torn between mathematical tripos and NatSci tripos at Cambridge university. Ultimately, I want a masters degree in theoretical physics( and not pure math), but I don't know if Natural Science would give the math I need. Also, I don't want to goof around experimenting (which is a part of NatSci). So far, Mathematics seems to be good ( I am only concerned about GR, my field of interest), but I'm not sure if it is possible to get a masters in theo. phys. after a BA in Math. Any tips?
But in your case, since you are more inclined towards particle physics, you could go to Utrecht. The Utrecht website is quite incomprehensible, so, I cannot help much more with it. In any case, my suggestion would be Glasgow. However, and this is the most important point, the Utrecht course is much more RIGOROUS. So, even though they won't give you much choice, whatever you do study there, you will get a great hang of it.