I was surprised to find that the petrol tank was about to fall out on my 2.2. Both lower straps had just about rusted through.
That's very common on a Murena (straps rusted through) and happened on my car many, many years ago. I replaced mine with some that were from another vehicle so that they actually contained some metal! :-) The originals were so thin even new that they were never going to last long... And in case you are going to ask, mine came off a truck and I had to modify them, so they were not a straight fit. You could almost as easily make some up from sheet metal.
However, as for the tank falling out, never! Have you ever tried taking one out? The tank might drop slightly once the strap has broken, but it would be impossible for it to drop out. You shouldn't, but you could probably drive a Murena for years with the tank straps broken.
Might be worth getting your own car on a ramp and checking....
Everyone should have checked these at least once a year at M.o.T. time! And if an M.o.T. tester misses them, he's not doing his job properly!
hoping to have a Murena on the road for the summer

What?! Is it not on the road now? What is wrong now Zac? :-)
Roy