Haven't seen it yet but hoping it will not "embarrass" my 'blad, lol ! I know London is not Aus but perhaps a search for Kaiser products might help you.
Hassys are weird b/c I've found some cable releases (namely cheap ones) don't fire them...even though the prong throw/length seems to be the same length as shutter releases that do work. Go figure.
Anyway, Adorama has a cable release, branded under it's own name, it's very nice, and reasonably priced for what it is. It's called their "super PRO cable release." And it has gold trim. All sorts of gawdy, but it's a good buy I think.
The advice around this town is Nikon. My slightly aged Fuji GM 670 wouldn't fire using a generic cable and the unhesitating advice from the vendor and a few others was Nikon. They were right. The only problem is the price, particularly when replacing a lost one (like all cable releases they love to fall out in long grass)
I have a bunch of Nikon cable releases that I use with my Hasselblad and Rolleiflex and I am very impressed by them, in contrast to lesser cables that have failed me. Nikon calls the model the AR-3.
I second AgX's suggestion (right from the manufacturer), and as already said, Silverprint is a good source too.
I bought this one from Calumet but don't like it much, because the head is too heavy and it always seem to hit something. http://www.calumetphoto.com/item/BR5120/
Back in the 70's/80's most camera manufacturers made cable releases. Canon, Nikon, Pentax, Minolta all made excellant quality cables. Most were the standard 12" length and have a very smooth action plus a lock for Bulb use. When I go to photo flea markets cables are one of the things I always look for, you can never have too many.
I found two old Kodak units in my favorite used camera store. They work like a charm in every shutter release socket I have including the Hassy. I bought a Fuji view camera lens that came with a Nikon cable release. It also works in every shutter socket I own. It's just a cable release. It ain't rocket science or brain surgery.