Yup, the simple life movement in the UK is alive and well. Hugh Fearnley–Whittingstall is the catalyst for at least some folks interested in getting back control of the food that they eat and feed their families. His site is a great resource for "Small holders" (the closest term to Homesteading in the UK) and has everything from husbandry issues to great recipes for blood pudding.
http://rivercottage.net/index.jsp
There is a really good UK magazine called "Permaculture" I wish I could get it stateside. Some friends of mine occasionally send me a few back issues.
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As for how is it different.. well, in many ways. Regulations there are MUCH stiffer in some areas... less so in others. Issues like slaughtering often become an issue where some folks can't even slaughter for themselves. (larger livestock) Other issues are land use. Farmland is farmland and can almost never be built on. Man has the right to walk the land there so often times there are right of ways through your land and you've got to build (or maintain) a stile to allow walkers passage. And of course land in general is much dearer that it is here. most small holders have much smaller properties that in the US. A half acre is a huge yard and I've seen many folks use every inch of those properties.
However, there are options even for city dwellers to do "homesteading" type things. Allotments (communal owned green spaces set aside for gardens) can be "rented" to produce a home garden from. These are taken great advantage of in the UK and spawn a rather odd social gathering place during the summer. Also, common greenways allow fore a huge assortment of wild harvesting. My family used to gather in our greenway nearly daily. Everything from blackberries to apples, elderberries, horseradish, hops, nettle, pear, crabapple and a host of other things.
It seems the majority of local producers have adopted a mentality of artisan producers which has turned the cottage farmer into a fairly profitable thing (since the big farmers are having a time of it there .. as they often times are here) this has seen the production of some VERY good things become available. It sells at a premium but you get what you pay for in this case. Everything from cheeses to wild boar are being produced by the small holder and the farmers markets which used to just be wholesale outlets for overseas produce are becoming wonderful gastronomic delights.
I look forward to that ideal spreading in the US as well.
The differences (and similarities) are large. If there are specifics you want to know just ask.
J