Electoral petitions: seats swapping?

I've looked at the Electoral Act to work out this swapping from a list seat to a constituency seat issue. My thoughts are as follows: If an (existing list) MP contests a by-election and wins, their party does not (automatically) gain any extra seats. The section which deals with when a vacancy is created (s55) is not triggered. There's no distinction in section 55 between constituency and list seats - you only have one seat in the House. While the reason why an MP is entitled to sit in that seat may have changed, that MP still only has one seat. The MP hasn't vacated their seat so there's no need to it to be filled by the next person on their list. However, if an (existing list) MP *resigns* in order to contest a by-election then a vacancy is created (s55(1)(f). The vacancy is filled by the next person on the list (ss 134 & 137). If the MP wins the by-election, then their party's numbers in Parliament go up by one. I'm not sure by when the resignation must be made by for it to create a vacancy but I anticipate if it before the results of the by-election are declared - which could be *after* the expected results are know. Similar possibilities arise if an (existing list) MP is declared elected as a result of an electoral petition. There is a potential anomaly in that once the list members are declared (based on the proportionality principle), then there is no automatic provision for re-computation of the list sits if there is a change in the constituency seats. There is some speculation that this means that Heather Roy may be entitled to remain in Parliament even if Rodney Hide was ousted from Epsom as a result of an electoral petition! However, there is a possible means to "cure" this anomaly . A party could file an electoral petition to the Court of Appeal under s258 challenging "the procedures and methods used to allocate seats to political parties ... and the return of members of Parliament consequential on that allocation". The challenge would be on the basis that the outcome of the electoral petition in a constituency seat affects the basis of the allocation. Of course, this means the electoral petition to the Court of Appeal would have to wait until the outcome of any High Court electoral petition - as the time limit for filing such a petition is short, presumably it must be filed in anticipation the a win in the High Court and stayed until that result is known. On this basis, I think then Heather Roy looks vulnerable if Rodney Hide was ousted and, I think, the reallocation of the 2% of the votes might favour the Greens and Labour (who are next closest to gaining extra seats). Therefore I think the possible scenarios are as follows: A. If there is a by-election and: (i) Peters resigned to contest it and wins it, then National loses 1 seat (Clarkson) & NZ First gains 1 seat (new list member plus Peters in Tauranga) (ii) Peters doesn't resign and wins it, then National loses 1 seat (Clarkson) & NZ First stays the same. B. If Peters is declared the winner in Tauranga in an electoral petition and: (i) no challenge to the Court of Appeal is made about the allocation of seats, then National loses 1 seat (Clarkson) and NZ First stays the same. (ii) there is a challenge to the Court of Appeal about the allocation of seats, then National stays the same (loses Clarkson but would bring in the next National list member) and NZ First stays the same.