Do you need to sell your house to establish non UK residence?
If you're looking at becoming non UK resident unless you are going overseas under a full time contract of employment you will be looking to establish a permanent departure from the UK.
In order to evidence a permanent departure from the UK if possible you should be looking to sell your UK property.
It is not obligatory to sell your UK property prior to leaving the UK in order to establish non UK residence. You should however make it clear that you have left the UK on a permanent basis.
Therefore if the UK property is up for sale and is not occupied by you (eg you have moved furniture etc) this should assist in indicating that you have made a permanent move overseas and occupation of the UK property is not intended to be part of your ongoing lifestyle. If after a period of time the property does not sell you could then consider letting it to reinforce the fact that you have no UK available accomodation.
Whilst it is unoccupied you should effectively 'close down' the house and cease to use or occupy it. Therefore your furniture should be moved overseas, the keys should be passed to the estate agent and telephone etc disconnected.
All the various utility companies should be informed of your emigration overseas. Post should also be redirected.
If the property does not sell within a suitable period (eg 6-12 months) you could consider leasing it. If you were still looking to sell and had high hopes for an early disposal a short lease may be acceptable.
If however you were looking to let the property for the foreseeable future a longer lease should be granted if possible to assist in indicating the permanent move overseas.