Help fixing a tap?

[London Gent]

My cold tap doesn't work - it just runs a dribble when turned on. When off, its off.

Do I need to change a washer? Maybe I need to replace the tap?

I got this far (see photo) however, when I use my adjustable wrench to try and turn the brass bit off, the tap body just moves with it....

Photo

[London Gent]

old tap doesn't work - it just runs a dribble when turned on. When

I cant get the brass bit off (still). If I buy a new tap, will I still have to remove that brass bit? May just replace the whole thing.

Under the wash basin: Wide view:

Don't know why I put these here. Maybe someone's got another tip for me.