can't access tap headgear to remove and change washer

[needtobediscreet]

we have a mixer tap in the kitchen that's dripping badly. I've changed washers on taps successfully in the past. I don't think I can post a photo from the mumsnet app(?) so will have to describe instead. tap seems to be a pretty basic model. the headgear on each side is horizontal / side-on, as opposed to vertical / accessed from the top, as I've dealt with previously. the actual tap covers most of the headgear so I can't
get an adjustable spanner in there tp remove the headgear.
any suggestions please, other than call a plumber and / or get a new tap?! ta!

Does it turn on and off with a quarter-turn, or does the knob rotate several turns between on and off?

Is there a cap or disk in the knob that you can pry out for access to the knob-retaining screw?

hi piglet
the tap goes from off to max ( and no further) in a quarter turn....

not sure about your second question - sorry, am being dim! thanks for replying.

to explain further, the headgear is kind of countersunk into a fixed
part of the tap that can't be removed.

Quarter-turn means it has a ceramic cartridge, not a washer.

Is more troublesome. If a major brand, a spare cartridge will be available, but you will need to take out and measure the old one.

I can't visualise your tap without a photo. If you can see a brass hexagon, a socket spanner might fit.

Thanks so much piglet! I had no idea about those taps. Not sure I'll manage to get the headgear
out. I can see the nut. It is hexagonal - and brass.