Our combi boiler normally sits neatly in-tolerance at about 1.0-1.5 bar. Noticed in the last day or two that it was sitting more between 1.8 and 2.6 (the panel states to call an engineer if it’s <0.5 or > 2.5).

I’ve just released air from one of the upstairs rads which has resulted in a drop in pressure to 1.8. All of the other rads appear okay, heat-wise.

Should i be concerned re the presssure creep or can I relax now?

Hmmmm. Might be a failing expansion vessel, probably worth testing it. When was the last time system was flushed and refilled? Might be some corrosion build up?

Lots of reasons why it might increase in pressure.