Tdabash has pointed out the matter of whether it is you who holds Japanese permanent residency or whether it was your wife who held UK permanent residency - the legal term is Indefinite Leave To Remain status when she last left the UK. I suspect its the former.
Do we have to prove that we have an accomodation ?
Yes you need to show the ECO that you have accomodation and yes your application can be refused on this ground although IMHO it is unlikley as the sole ground. As per tdabash's comments it may be best to contact relatives or friends and ask them to provide written confirmation that they will provide you with accomodation whilst you find your feet. They must provide evidence of right of residence in the form of mortgage deeds or tenancy agreements. Where its the latter a consent letter of your stay from the landlord will be required. They must also submit a utility bill e.g. telephone or a council tax demand. There is less scrutiny of an accomodation offer where its from a relative to another relative. Where the person offering the accomodation is not a British Citizen the ECO will also want details of their UK immigration status so you need to supply a copy of their passport biodata page and the page with their immigration stamp. One thing the ECO may focus on is the size of the house to make sure there is no overcrowding.
I usually recommend people to also combine the above with their own accomodation search e.g via the internet. Type into google 'accomodation in x' where x is the area you are moving to in the UK - I am sure after Japanese property costs the UK will be fairly cheap unless you are intent on Chelsea. Alternatively do the same web search for an estate agency and arrange short term accomodation e.g. 2 months. Get the agency to fax, send or even courier the tenancy agreements. They may be even able to get you short term lease/ guest house type accomodation. Again I think the ECO will be less likely to be concerned about short term accomodation issues if you have substantial funds in your possesion when returning.
If it is your wife who had ILR when you left the UK then she would be deemed to have lost it as she has been outside the UK for more than two years continuously. An application for a returning resident visa will thus be refused and an appeal will just be a waste of time because the appellate authorities will agree with the ECO. The only way she may be successful is if she has spent a longer proportion of her life in the UK than out of it. In any case once the spouse visa is approved she will be given Indefinite Leave To Enter and thus get her PR status back so the matter of a returning resident visa is moot. The spouse visa must be applied for on Form VAF2.
and what kind of evidece are there to prove settlement in the UK?
Settlement means that you have the right to enter, live and work in the UK without needing permission from the immigration authorities. Your status as a British Citizen is proof that you are settled. Note that the Immigration Officer at a Port of Entry when checking your passports is making sure that you are entitled to be admitted on a settlement basis and that no further inspection is required.
As a side issue you may wish to consider obtaining Japanese citizenship to facilitate your future travel into Japan or even residence as the case may be. As you note from the UK's 2yr returning resident criteria permanent residency can be lost when you are away from the issuing country for a long time.
You may wish to review my earlier posts to
tdabash and
Ge on this forum to get a further insight into the accomodation, maintanance and associated issues for family immigration.
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