As L&M says.
Feeding concentrates to Hebs over the winter doesn't help them to finish quicker - just costs more. They only seem to finish well on grass - we send ours off at 16 months (as recommended by the Hebridean Sheep Soc) which for us means the beginning of August, a couple of weeks before weaning the next crop of males (we let the ewes wean their ewe lambs). We only feed concentrates (for us - Carr's Champion Tup mix which is safe for both sexes) to tup hoggs when there is snow on the ground or a hard frost (which is quite often here

) but they do always have adlib hay and a licky bucket, plus water of course, throughout the winter months. They start to grow again when the grass does.
We used to send them off in June but found we still had some low weights, so now we wait until August and have been pleased with the results.
Heb Hogget is a different product compared with downland breeds but everyone I know who has tasted it loves it
I see no point in bringing them in to try to fatten them quickly - they are a hardy outdoor breed and the meat tastes that much better for growing slowly.