Chris wrote:

I'm considering concrete beam and block to replace a suspended timber
ground floor. Can anyone give an idea of the cost comparison for
concrete and timber. I'm only looking at a room size of about 4m x 5m.
Thanks, Chris.

If DIY probably cheaper. Contact travis perkins for a quote.
You need to get the beams made specially to size.

However its usually cheaper to just chuck hardcore and cement down and
then DPM and screed. Any reason for suspended? BCO insisted in my case
due to large areas/wet clay/presence of tree roots etc.