InTheHills, for condition scoring for Soays I second what Fleecewife says - I've never felt one that had reached 3 on the conventional scoring system. Even the one that was a handreared orphan who at times looks like a barrel you can still feel all the bones in her spine very clearly.
I generally check their condition by eye. Look for the hip bones becoming prominent and also their stance. If they are losing condition they tend to stand with their back arched and their back legs bent and 'tucked under' a bit. Take particular care with any with particularly thick fleeces, they do vary quite a bit, as they can look in better condition than they are. Picking them up is a good test - especially for lambs.
At this time of year we feed mainly ad-lib hay with a small quantity of ewe nuts and we also have mineral licks out. We don't lamb until April-May (
)so by the time they are approaching lambing the grass is ususally taking over from the hay. We increase the ration of nuts a bit but nowhere near what the books recommend for a 'standard' flock. Do take care not to overfeed, as the lambs can get to a size where the ewes struggle to get them out. If you get the balance right you will rarely have to help at all.