Is it possible to be self employed (officially) and then to also work part time for another company to supplement you income?

Yes.
I work part time for an events company when my own trade is quiet & I invoice them as a freelancer under my self employed business name.
Obviously the company for which you work will have to be OK this as well.

Leafy says it all. You are allowed to have a second job.

As a notice though: you need to be extremly careful if your self-employed work is in the same field as your regular work: concurrency rules apply and you might loose your job because of it. Make sure to contact your company in this case. If it is in another field, you don't need to worry.

There is an issue with income tax deductions though: If the regular employment position takes up 50% (this figure may vary) and above of your time, then you may not deduct any expenses to offset earnings from your self-employed position.

I am pretty sure ou can deduct 20%, even the RAV allow a 20% reduction of self employed earnings when calculating your monthly pay out if unemployed.

If you're unemployed and thinking about starting your own business, you might want to check with RAV if it is OK. You might loose your unemployment money.

Well this seems to answer some of my questions about my intentions at the moment. I work part time for a school but have set up my own business. My wife is currently unemployed and we are both being supplemented by the Chomage/RAV. I'd really like to get a cash settlement for our pensions and the only way seems to be by being self employed.

I am hoping to declare myself self employed(need to read more threads for how to do this) then work freelance for my current employer and then ask for my cash settlement. Once I get my cash settlement then I am going to make plans to return to the UK.

I looked at using it to invest in a home in the UK but it looks very complicated. If this all works out I'll be over the moon. So chances are that it wont

So far as I understand if you leave CH you can ask for a cash settlement of your pension; you do not need to add the complication of being self employed. Unles there are special circumstances

Yes you can but my pension is with Zurich and they'll only pay out if the UK say I am not part of a compulsory pension scheme. I'll no doubt pay National Insurance so wont be elligable

National Insurance is not what they are talking about, a company pension scheme would be.

You sure? I can work supply and avoid a teachers pension scheme easily I suppose. I've decided to buy a house in the UK. However, some Swiss companies pay out and some don't. Spoke to my current pension company today, they wont pay out so have advised me to transfer my pension back to my original company (libre passage) when my current job is finished. The original company do pay out if I buy a house in the UK. So just make sure you ask your pension company in advance and work out if you need to change it.