MPs can be recalled. en.wikipedia.org/wiki/Recall_of_MPs_Act_2015#Recall_procedure
Constituents can use it in certain circumstances (C&P from Wikipedia):
- A custodial prison sentence (including a suspended sentence)
- Suspension from the House of at least 10 sitting days or 14 calendar days, following a report by the Committee on Standards
- A conviction for providing false or misleading expenses claims.
Two MPs have been recalled and got rid of using this procedure.
Fiona Onasanya, Labour, after she got a custodial sentence for perverting the course of justice for lying to police to avoid being prosecuted for speeding.
Christopher Davies, Conservative, after he pleaded guilty to two counts of fraud concerning parliamentary expenses.
In Hancock's case he'd have to be suspended for long enough (as above) and then (Wikipedia again):
Once one of the conditions outlined in the act is fulfilled, the Speaker informs the petitions officer of the constituency (in most cases this would be the returning officer or acting returning officer). The petitions officer is then required to make the practical arrangements for the petition so as to open the proceedings within ten working days after the Speaker's notification. This involves selecting up to ten signing locations where petitioners can sign in person, these function in a similar manner to election polling stations.... The petition remains open for six weeks. No ongoing tally is reported by the petitions officer and it is not revealed if the required threshold of 10 per cent of eligible voters threshold has been reached until the close of the petition period. During the petition period the MP remains in office. If the petition is successful the seat becomes vacant and by-election procedures begin. The recalled MP is permitted to stand in the by-election. If the MP vacates the seat, or a general election is called, the recall is halted and the petition ends.