Thanks guys. I went on a course about pig-keeping last summer, so know a fair bit about the basic requirements etc, but have only just got to the stage where we are moving somewhere suitable to actually be able to consider getting some. The garden is a good size and not directly adjoining any neighbours, so don't think smells/noise etc would be an issue. I am also renting an acre next to the property, but am not keen to run the pigs on that as it's obviously not my land, so am assuming the owner would be unamused by pig-activity there and would prefer something that grazes rather than roots!
As a result I was planning to keep that land for other livestock, but am very keen to have a couple of weaners and, as the garden is my own land, it's up to me what happens to it in terms of mess! I realise that the more space the better, but from other things I have read in the past, it seemed possible to keep them somewhere small-ish, provided the fencing is good and they are only there a very few months. If I did this only once a year, the ground would have chance to recover in between, with a bit of tlc and re-seeding. At least, that was my thought.... But obviously I've never actually done it, hence my request for ASF people's wisdom and experience!