@ Laura,
You are right on the fact that the shop is a experience that one should do. It is very welcoming, lots of magazines to read, lovely tanks to look at and very friendly people. Had the shop be in London it would be full day in day out, they could even serve coffee and charge for it.
Regarding the rocks, there are items on stock for all tastes, and some rocks are indeed large, and must weight more than 100kg for sure. If TGM just sold tank decorations they would still be an amazing shop. Pitty that it is an 8 hour round trip from London...
If for you it is ok to pay more than twice as much for the perfect piece of rock, then you will be in your perfect environment, as there is no way you cannot find what you want at TGM, it is just impossible. You will even find what you didn't think you want or needed..
With hindsight would I have paid the £6.75 per KG for the rocks I got? My head says no, but my heart says yes.
The 6kg of rocks I got are more beautiful that anything else I got on my tank, and being rocks they will last forever, I am not even looking at the plants, just to see the shrimp walking along the rock wall is mesmerizing.
In 20 or 30 years time I will look at them and think about the fantastic trip I had with some plant nutters to the end of the earth to look at acrylic tanks, a shoal of Altum Angel's and have coffee served within ten minutes of walking into a shop.