I've bought some spiral saw blades from these guys in the US and they cut much better than an abra file did and the blades seem to last well. I've sawn some 3/8" black plate with one without a problem.
They go into a special coping sawframe or there are longer ones that go into a standard hacksaw frame.
They do have clips on theends but you fiddle them off to thread them through a small hole.
Not that cheap, (about $6each) and I paid a bit of import tax to UPS, but a great solution to any direction cutting.
No UK distributor but you can buy direct from theirUS webshop http://www.bestwayproductscompany.com/
Maybe Ketan would importsome if demand was big enough?
Just a satisified customer, though they did send me a spare blade 