Further to the explanation given by
buildersmate and the argument used by
joko, adverse possession (squatting) is perfectly legal in specific circumstances,
however...
You cannot force entry into the house since Breaking and Entry is not squatting, it is trespassing. If this was not the case someone could break into your house every day and claim to be squatting. The police have powers to remove trespassers immediately so long as the evidence of forced entry is still present.
Uk law concerning adverse possession may in itself be unlawful in regard of the European Convention on Human Rights.
A recent decision by the European Court in a case involving 56 acres of grazing land in Oxfordshire was that it would breach the human rights of the original owners if the title were to pass without any compensation being paid.
http://www.hancockcaffin.co.uk/news/.htm