Seperate Residential mortgage for husband and wife

Dear MSE members

This is my first post to the forum. I have been a silent follower and active user of MSE and appreciate the contributions. Now I need some help and though the lovely fellows here will have some input.

I live with my wife in a rented accomodation and both of us work full time.

My wife wants to buy a house on residential mortgage as sole ownership which she will pay for (deposit+mortgage installment etc). I intend to live with her for now. But I do not want to be on the mortgage or any sort of documentation for several reasons like I want my credit history not affected by this, I want open choice to have my own mortgage and I don't want relationship changes affect anything.

Our marriage is not registered in the UK but another country. I am not sure what constitutes a 'legal marriage'.

I want to know:

1. Do I have to be named on the mortgage she takes? (as contributor)
2. Do I have to be named on house title as a tenant and how does it affect me and my mortgages in future?
3. Can I buy a house on my own name as residential mortgage at later stage, let's say 2 years later? I will live in it time to time as I need my own space sometimes as I am home based worker. I might also want to rent it out.

I have been told you can not get separate residential mortgages which sounds odd to me. If both of us earn good enough to afford it, why not?

I would like to know what the actual situation is. If its not possible, what are alternatives or workarounds. I know there are always those loopholes and ways to avoid funny laws.

All help much appreciated.

Thanks
AM