I do have an expatriate contract and it appears that I am eligible for the Expat Tax Allowance as long as I don't rent out my UK property while living in CH.

As the rental income from renting out my flat in the UK will most likely be higher than what I'd get from the Expat Tax Allowance I'm going to go ahead and rent it out.

Thanks to Greenhill for the suggestion to get in touch with the tax authorities in Lausanne. They will be a useful resource for the hundred other tax related questions I'm sure to come up with.

Many thanks,

Charday.