Thanks for the tips! I might look into a hoof supplement as I feel bad that his feet (to me) look in such a sorry state right now. At the end of winter he developed horizontal cracks across his coronets on both back feet, the front were affected too but not so badly - the vet thought it was a mild laminitic bout due to the change of seasons as nothing showed up in his blood test.
The new hoof that is growing down looks pretty messed up and my farrier is concerned that there will be trouble when the new growth (which are no longer deep cracks) gets further down. I will get some pics this weekend to see what people with more experience think, the farrier is due this weekend for a trim so will see what she says too. I just feel awful that his hooves look so bad at both ends, breaking off badly around the edges and some funky new growth at the top! I have been reading as much as I can on hoof care to get some more knowledge but will admit that I am still quite new to it all.
In the past I have had horses with great feet so really left it up to the farrier (no excuse I know but was much younger then and didn't need to do more than keep them clean). Will also see if she can show me how correctly smooth them off between trims to keep the breaking to a minimum. Have just emptied his trough and refilled it so the ground is nice and wet for now but in for another scorcher tomorrow so wont stay wet for long.