What are my options?

[rapalaman]

Just a bit! Enquired about a pallet with tirfor on a pallet from Scotland to here and was about £100 ☹️

[djbobbins]

If you want to fill it with as much mass / as few air gaps as possible, could you not crush the storage heater bricks? Alternatively it’s possible to buy sacks of ready-crushed firebrick grog.

[openspaceman]

14 minutes ago, djbobbins said:

If you want to fill it with as much mass / as few air gaps as possible, could you not crush the storage heater bricks? Alternatively it’s possible to buy sacks of ready-crushed firebrick grog.

It would be interesting to see and I don't know what those heat storage bricks are made of but generally when you crush something it takes up more space. A bit like chopping a log, the resulting pieces can never be fitted back together in the same space.

 

Think about how the ballast in concrete is stones of various sizes and then sand to fill the gaps, the cement then fills the remaining gaps and displaces any air.

 

I'd use the biggest sizes and fit them as accurately as possible then sand  to make the thermal connection, then the bricks can be removed in the future.