Thanks for the further suggestions (and advice on the dry pump to warm the group head )

The lever is the right way up. There is some play side to side but I try to keep it centred when pulling the shots.

I will check if the piston head came slightly loose.

My wife also mentioned that it is much hotter in London now and ambient temperature / humidity could have a big impact. Do you think that might result in needing to grind much much more coarsely?!

Cheers,
Adam

Your wife is probably the winner here today. Make her a special cup.

It could be a change in atmospheric pressure and that high humidity. Definitely makes me alter my grind fairly often surrounding summer storms. Never really did much in the west though where it is drier. Where I live now is high humidity as a rule and just goes higher, or so it seems.

Another possibility... Did you wipe the piston shaft clean while you were servicing the machine? There is a piston shaft gasket hidden up inside the group that needs to remain lubricated. A dry piston shaft and gasket would lead to some serious stickiness.

Thanks all for the suggestions! The main thing that has helped has been replacing the portafilter basket (2 yrs old).... despite descaling it maybe some fine grounds or other build up seemed to be causing resistance. Morning coffees are much better again! Appreciate the support from this great community