Lots of great info, I just have a couple of things to add. (I know this is an old topic, but wannabees and newbies will read old threads as research, so still worth posting
)
I have a saying, 'Hay maintains condition, you need grass or good haylage to make
milk". This is true for both cattle and sheep to my certain knowledge, I'm not experienced with goats. Your ewes will struggle if you expect them to feed themselves and their lambs on just hay, and the lambs will struggle if the ewes can't make enough milk. (You can also buy expensive concentrates to increase milk yield if you lamb in winter.)
Cows (Dexters) - eventually - 2 adults and 2 young to replace them.
This catches a lot of people out.
Dexters are no size at all until after two summers at the very least. Two cows calving every year very soon means you have 6 or even 8 animals on the site. Cows plus this year's calves, plus last year's calves growing on, plus two years' ago's calves to go off at 20-26 months.
As you are wanting milk, what about using the cattle for milk? Get Jerseys, or a Jersey and a Jersey cross, or two Shetlands, or similar. We do the former, use a good beefy bull - Angus or North Devon - and the calves are big enough to go off at twelve months or slightly younger. Officially the meat is "rose veal" and it tastes tremendous.
Jerseys would need housing over winter (or at least very good shelter if you are somewhere less inclement and less muddy than I am in North Cornwall; I've seen them living outside year round on well-draining ground in East Somerset and in Dorset), you might be able to keep other breeds out year round.
As well as hardiness to wet and cold, you don't want milking animals trailing their udders in mud as it would result in mastitis.
Dexters are extremely hardy, and you can get Dexters which are tame enough to milk, but you would still have the issue of the calves taking two summers plus to get to butcherable size.