Thanks Farfallina, I made these last night and they were a big hit!  I never would have bothered making these myself in the past (too easy to just pick them up at the chicken shop), but these were so quick, and it's wonderful and very satisfying knowing exactly what has gone into them.  I used mozzarella as that was all I had, and also only had one leaky one 

I've been a little slack in posting but this was the first 'meal' (after the obligatory custard and sorbet of course) that I made and we were throroughly impressed, it was absolutely delicious! 
Being a novice, I was a little too concerned with breaking the mince up (lesson learned) so it was a little fine, and my tortillas looked a little dodgy, but once it was all put together you couldn't notice that at all.  I also think that the home-made tortillas made all the difference, and am going to invest in a tortilla press - I never knew such a thing existed - thanks JulieO! (Actually, it was your enthusiasm and photos that convinced me I needed a thermomix in the first place - without having laid eyes on one - so thanks for everything!)