So I thought I’d give the reverb a bleed as I was having to depress the remote lever all the way to get it to move.

Once pressed most of the way the seat post would shoot up, and if I used the speed adjuster to slow it down it would really slow things down.

A little air came out when bleeding. All good I thought.
However the seat post now flies up extremely fast regardless of the speed adjuster setting.
If I try and slow it down nothing happens.

Have I done something wrong?

Had you wound the adjuster all the way to the “slow” position before bleeding it?

Yes I did that. I’ll repeat the cycle again and see if it fixes the problem.