But by your own admission you have overloaded your shocks with paving slabs
original shocks only last 80-120k depending on previous use, and don't forget that you reused the mountings last time which have recently failed... So hardly fair to criticise the parts for failing following abuse and neglect 
Paving slabs? Wtf! Never gone in my 2.2!

You do come up with some random crap?

So now it's 80-120k that's a big range. As per Webbys experiance, it's worth trying others.
I'm going with Meyle, see how they last.
Also as I say, read quite a few reports here that GM shocks not lasting like they used to.
My MV6 dampers lasted 13months before a failure on one of the rears, not long after the other followed, mileage was under 12k and has never carried any more than the weekly shop.
These are made by Sachs and I`m not at all impressed with their dampers anymore, I had premature failures on my Senator too 
12k. Wow. That's not good. TheBoy also reported poor life from MV6 shocks too from GM. He is much happier with B4s - but they are not for me.
Hence these Meyles look good, if they are anything like their droplinks it's a winner.
As GM droplinks are not what they used to be, very poor life span.