Grey Area help!

[Hbiz]

Hi, will try to be brief in explanation! Have called ukvi and been variously fobbed off and sent around the houses with no one willing to offer any help or advice!
I am British, partner is Australian. He entered uk on a partner visa as first stage of 5 year route to ILR in dec 2015. He has a residence permit which is due to expire 15th Sept next month. We are all moving to Belgium next month-he has a job and a Blegium work permit and long term visa and will not be applying for the second stage of ILR.
As I am British and we have a son we will however be returning to the UK regularly to see family etc.
And more importantly during September he will be travelling to and from Belgium until we complete our house move.
My question is, if he for example arrives back in the UK on sept 10th and stays past the 15th is he deemed as overstaying his visa? Should he enter the UK on the 10th as an Australian visitor without showing his residence permit and so have a visitor stamp in his passport? We are trying to pre empt and issues at immigration and also to prevent any potential bans!! Should he carry his Belgium contract with him!? Please help!

[The Station Agent]

From my POV he could enter as a visitor on that occasion and in future.

[secret.simon]

Visitors are not allowed to make frequent or successive visits to the UK (Rule V4.2 (B) of Appendix V of the Immigration Rules). It may be better for your spouse to not return to the UK after the partner visa expires in September.

The Immigration Officer at the border/airport may refuse him entry if he attempts to return to the UK as a visitor immediately after he has been resident here for more than two year OR if s/he feels that your partner is making repeated visits to the UK and attempting to reside in the UK in the guise of a visit visa.

Should he enter the UK on the 10th as an Australian visitor without showing his residence permit and so have a visitor stamp in his passport?

His residence status will almost certainly flash up on the system when his passport is scanned and he will likely be asked to produce his BRP or be refused entry.

Get him to do all that he needs to do before 15th September and hand over to you what needs to be done afterwards.