As with all constitutional questions in the UK, the qualifier "Parliament can change the below at will" must be borne in mind.
is there any process to expel an MP from their post except for calling a General Election, assuming no wrongdoing by said MP?
No. To my knowledge, the only mechanisms through which an MP can be pre-emptively removed from office rely on said MP committing some act of wrongdoing, and cannot be triggered without that condition being met.
There are a number of modern acts which define means through which an MP may be removed upon committing some wrongdoing or other. Section 2 of the Representation of the People Act 1981 automatically removes from office any MP who is sentences to a year or more in jail for any offence:
A person found guilty of one or more offences, and sentenced or ordered to be imprisoned or detained indefinitely or for more than one year, shall be disqualified for membership of the House of Commons...
(1) If a person disqualified by this Act for membership of the House of Commons is elected to that House his election shall be void; and if such a person is nominated for election as a member of that House his nomination shall be void.
(2) If a member of the House of Commons becomes disqualified by this Act for membership of that House his seat shall be vacated.
Similarly, the Recall of MPs Act 2015 allows for a constituency to recall its MP and elect a new one (or the same one again if they want to!) It's quirky in that the recall is subject to 10% of constituents signing a recall petition, but that petition cannot be instigated by the constituents themselves, rather it is automatically begun if any of the following conditions (defined in Section 1 of the Act) are met:
The first recall condition is that—
(a) the MP has, after becoming an MP, been convicted in the United Kingdom of an offence and sentenced or ordered to be imprisoned or detained, and
(b) the appeal period expires without the conviction, sentence or order having being overturned on appeal.
The second recall condition is that, following on from a report from the Committee on Standards in relation to the MP, the House of Commons orders the suspension of the MP from the service of the House for a specified period of the requisite length.
A specified period is “of the requisite length” for the purposes of subsection (4) if—
(a) where the period is expressed as a number of sitting days, the period specified is of at least 10 sitting days, or
(b) in any other case, the period specified (however expressed) is a period of at least 14 days.
The third recall condition is that—
(a) the MP has, after becoming an MP, been convicted of an offence under section 10 of the Parliamentary Standards Act 2009 (offence of providing false or misleading information for allowances claims), and
(b) the appeal period expires without the conviction having been overturned on appeal.
So the long and short of it is that a custodial sentence following conviction of more than a year automatically 'defrocks' an MP. Shorter custodial sentences and other misdemeanors might result in defrocking, but only if the constituency votes to do so. Parliament itself cannot remove an MP through these mechanisms; they can simply send the matter to the constituency in the form of a petition, by Suspending the MP for a period of 10 or more days.
Bonus fun fact: Parliament can actually technically impeach...anyone they please1, for any reason they please:
Resolved, That it is the undoubted Right of the Commons in Parliament assembled, to impeach, before the Lords in Parliament, any Peer or Commoner for Treason, or any other Crime or Misdemeanor
It works similarly to the US version; articles of impeachment are determined by the Commons, and the accused would be tried by the Lords. Given there's no limit afaik on the punishment that the Lords can impose, they could theoretically pass a custodial sentence in excess of one year and trigger the MPs automatical disqualification under the Act cited above, but in reality this is an obselete power that has not been used since 1848 and so is likely to be legally inoperable.
1: This is a scan of the House of Commons Journal; like Hansard, but different.