2014 Vauxhall Astra often gets stuck in gear,

Could be a hydraulic problem , check the master cyl level and for any signs of leak at pedal push rod . If not may be general clutch assembly wear entailing replacement .

On closer inspection, the reservoir was not full (could not say how low as not able to see into/through the white plastic container). But removing the top could see it was not full. Stupid positioning of the reservoir, not easy to get to in order to remove the top and not enough light to see the level. At a quick glance it looked OK!!
Nipped to Halfords for some fluid to top it up, and while parking experienced clutch drag whereby the car crawled forward while in gear and clutch depressed.
Now fingers crossed the problem is fixed and the reservoir stays full (i.e., I do not have a leak), worrying that the reservoir also does the brakes as losing those would have been dangerous.
On the other hand if clutch problems show up first it is a good early warning! But the level warning light on the dash did not alert me to the problem, although it does illuminate for a few seconds when turning on the ignition (as they all do).
I cannot recall ever having to top up brake/clutch fluid in 30 years of owning cars.

Update Dec 2021
Finally got round to booking it into Vauxhall dealer, total waste of time, they said they could not 'see' any issue, no leaks etc (I could have told them that!, indeed I did!).
They reckon they will have to take the gearbox out and would need the car for a week.
I think it is timer to go back to small local garage.

Hi, just wondered if you got this sorted as I’m having the same problem & already had new clutch fitted. Thanks

I’ve been having the same problem with my Astra K 2016 have had the gearbox and clutch replaced . Have been driving it for 3 weeks and it was fine and the same issue is back. The gear is getting stuck have the clutch fully pressed down and unable to take it out of gear. Happening in 1st 2nd and Reverse. Can anyone help.