On 05/12/2016 17:26, Simon T wrote:
[...]

Having difficulty tracking down replacements and if I've read the
description on the Dimplex website correctly, replacement insulation
panels seem extremely expensive (unless I read the wrong part).

The material is a ceramic fibre board and yes, it is quite expensive.
If you were looking at a retail price list though, the price would be
further inflated. Enquire through a an electrical wholesaler, or an
online spares supplier such as TD spares, for better pricing.

So, any idea how to improvise a suitable replacement sheet of
insulation? Needs to be fairly thin (about 1/4")

I'd advise against any improvisation here on fire safety grounds; the
core temperature of a fully charged storage heater is extremely hot -
hundreds of deg. C. Do you want to take the risk?

--
Andy