Ed wrote:
Just bought a new hose, but the thread on the tap connection is
slightly different to the thread on my outdoor tap, so it sprays
everywhere.

Make sure the rubber washer is in place, and suitable.You might need
different or thicker one.

What is the best way around this? I presume the thread on the hose
connector is standard and the tap I have is old and sh1te.

The tap is very likely indeed to have a standard thread, no matter
how old (well, at least 1/2 a century). If the plastic connector
goes on without splitting or the threads being chewed up, that's
not the problem.

The hose is
too thin to go over the tap nozzle, so I cant just go for the old
jubilee clip around the hose trick.

Can you warm the hose up to expand it? You'll probably need a gas
flame, used carefully. Your cooker or hob would do.

Are there adapters for this kind of thing, or do I need to replace the
tap

It sounds as if you've got two already (3/4" and 1" BSP)!