For my references, do employers in CH look for a letter to accompany your CV or just names/telephone numbers our your previous employers to call them?

For my current employer, is it ok to ask a previous supervisor to provide me with a reference as I cannot obviously ask my current supervisor for this!?

Both a letter or contact details of your direct supervisor are acceptable, no colleagues nor friends references

I would not attach any letters or details of references to your CV when you apply... wait for the prospective employer to ask for them. You can put a "References available upon request" line at the end of the CV.

And, of course, make sure you have warned your referees to expect a call from this particular company - not only out of politeness, but also to brief them on any specific things they may be asked about in relation to your fit for the job.

For my previous employer which was 8 years ago, I mailed the woman from HR. None of the people I worked for are working there anymore so she wrote me a letter of recommendation. Would this be ok?

My previous supervisor is really sound and a great reference to have, I get/got on great with him so he will give me a great ref when the time comes. I've aready asked him.