Looking to purchase some cladding for an external building (approx 50 sq m)
.... Western Red Cedar would cost close to £6.5 per linear m .... which makes
it very expensive to clad.

After looking at other options ... been suggested I use Finnish Thermowood
http://www.thermowood.fi/data.php/20...w_handbook.pdf

Not cheap, but better priced than WRC.

It should perform much better than plain softwood cladding.
What I want to avoid is a cheap shiplap that splits badly as it ages (i.e'
like that on a B&Q shed)

Anybody any experience of Thermowood