leaking shower tap

[rulh1]

My shower mixer tap has had a leak for a while now – hot water – but getting worse.
Tried to fix it yesterday but got totally stuck!

Assume there is a circlip on the spindle that stops it pulling out but could not find one.

However, did find a small screw in the middle of the spindle, which when undone revealed a further screw inside the spindle. Undid this as far as it would move (almost as far as the top of the inside of the spindle), but it did not release the spindle.

There was some movement in the spindle – it came out just about far enough for me to feel a slip ridge on it.

Have now tightened everything back up – and have a regular drip coming from the inside of the spindle.

What am I missing?

Apologies for the lack of technical info!

I was pondering changing the present mixer to a thermostatically controlled bar shaped one, but I’m not sure how practical that would be

Thanks in advance