You won't be able to get on a plane with an expired visa vignette. You need a new visa vignette.
https://www.gov.uk/guidance/coronavirus ... -residents
If your 30 day visa to work, study or join family has expired
If your 30 day visa to travel to the UK for work, study or to join family has expired, or is about to expire, you can request a replacement visa with revised validity dates free of charge until the end of this year.
To make a request, contact the Coronavirus Immigration Help Centre. You’ll need to include your name, nationality, date of birth and your GWF reference number with ‘REPLACEMENT 30 DAY VISA’ in the subject line. If you’ve already contacted us about this, please let us know in your email.
You’ll be contacted when our VACs reopen to arrange for a replacement visa to be endorsed in your passport.