Could you attach a piece of clear acrylic sheet over it?

Less than 18 months after installing a new kitchen, one cold winter night when a large cast iron pot was on full heat on a corner gas burner, our silestone counter cracked (see photo). The counter material was silestone provided by Cosentino. Cosentino came to inspect the damage but their engineer claimed almost as soon as he entered the kitchen that their (25 year) warranty was invalid. He claimed that we must have put hot pots on the adjacent counter, which must have weakened the material making it susceptible to thermal shock. They have however offered to replace this part of the counter if we pay them £3k. We suspect that this damage is the result either of material weakness or poor layout design but are looking for an independent assessment to give us an honest view of how this happened. Can anyone recommend someone with relevant expertise in the London area who we would be able to hire to provide an independent assessment?

I took your advice @alyson38 , @Fran and @Raumtastik and here is how it looks so far. I havent finished painting walls which will be SW Alabaster. I am currently trying to decide if I should do open shelving on either side of the kitchen window (I put some blue painter's tape where it would go) or some blinds (in natural wood looking woven linen, bamboo). It needs something there as it looks kinna blah.

It is probably better to keep to one height in the sink corner, for all the above reasons. This time round I'm going free-standing. I discovered one height all round affects my shoulders - the worktops are too high for my height and different jobs (eg mixing, bread making, carving, chopping) and it seems there's a standard height just to fit the appliances underneath. My current, old, about-to-be-redone kitchen served its purpose but practically didn't work so well. So this time I'm including working heights that suit me, not the designer \ trader.