MATZ
I agree with a previous poster that they will generally prefer it if you route via their overhead at virtually all MATZ that I have been to. IN areas such as the Vale of York or through Lincolnshire they will certainly pass you over from one to the next as a matter of course. However, what they are really doing is making sure you are on some obvious routing that they understand and also keeping you clear of landing and departing aircraft.
Here is some advice for the original poster who is new to the MATZ. Firstly don't forget they will give you a QFE and you will fly that height. Secondly listen to the tone of the response and be prepared no to fly through the MATZ if they tell you they are "hot" or otherwise sound as if it is a bad idea.
Here's a really controversial remark for light aircraft. Try flying above the MATZ! It's amazing how many prople fly around at 2-3000 ft even on lovely days. As long as you stay out of the airways go as high as you can.