Some good advice has been given here regarding the need for caution. UK law allows you to use "reasonable force" to defend yourself or others. Trouble is (what a surprise), no-one will (or can) say in advance what the police, CPS (about the equivalent of DA I think), judge or jury (crucially) will think of as reasonable.
There has been considerable debate about changing the law to give householders the "right" to defend their homes, families, etc. without fear of prosecution. The government declined to do so, instead opting to "clarify" the meaning of the existing by means of examples.
I found this quite helpful in that the examples did make some aspects clear (this is the link:
http://www.cps.gov.uk/publications/prosecution/householders.html).
But, I think it would be a mistake to assume that you would be regarded sympathetically "if you use something to hand as a weapon" and that something turned out to be an
actual weapon (bow, firearm, sword and especially anything that is illegal to own, such as brass knucks, handgun, taser, H&K MP5 etc.).
I recall hearing a senior cop saying (more or less) that it was OK to have a baseball bat (not a cricket bat, funnily enough) by your bed just in case, but you'd be on thin ice with many of the weapons suggested (spears, for example). If you live in a town or city and don't have a demonstrable (and mundane) need for such things as a machete or a Granfors Brucks double-bitted throwing axe, you will probably be assumed to be a psychotic, sociopathic hoodlum and prosecuted accordingly.
I agree that UK law in this regard leaves a lot to be desired and I would give more weight to the safety of my family, friends and any other innocents than to some stiff-arsed CPS lawyer and their idea of what constitutes reasonable force. Some (most, in fact, I would think) of the "people" making decisions about this sort of stuff probably haven't been in any sort of ruck since that time at primary school (where they ran away crying to teacher after some girl pulled their hair)
Having said that, *** is this "nerfland" business? Does it have something to do with the UK being "socialist" (as someone in another thread claimed)?