Hi duchesse
It varies from one local HA to another, but where I am (East Mids) over 35s are offered a nuchal scan at 12 wks, amnio/CVS thereafter if the odds are over 1:250, and triple bloods at 16wks. They're all discretionary of course. Some HAs don't offer the same and you may have to go private, which is a bind. You'll find a variety of approaches to testing on this and other threads - some women definitely wanting the lot, others wanting none, others going for the non-invasives but drawing a line there, etc. etc. In terms of chromosomal issues, the NT scan gives odds for Ewards and Patou as well as Down's, but of course they can't test for everything (including lots of conditions which will result in having a child dependent on care eg spectrum disorders). Nothing's foolproof!
The most quoted stat for miscarriage risk for amnio or CVS is 1%, not 10% - hope that's not your local stats!!
By age, my Down's odds were 1:60, by NT scan they were 1:322 - which means there's a 99.7% chance of my baby NOT having Down's. So I didn't bother with the bloods, and would only have done so to 'be prepared' in any case. Others on this thread have had much higher odds in favour of Down's but no babies had it.
Hope that helps, and that you can access what you need where you are.