and this is why i discourage friends from reading too much stuff on google. It can send anyone into a state of panic if they read up on something and cant get the correct advice they need. I did exactly same thing (for different condition) when i was pregnant and eager to learn everything i could.
Were there any other markers? I have no idea what an 'echogenic foci' is but other markers for a baby with downs would be on the nasal bones and the nuchal fold as well usually.
What did the consultant say about the foci? are they concerned in any way (not just for Downs) are they offering more scans later on?
The blood tests will only give an indication of the risk. That doesnt mean to say that if you were a 1 in 5213 chance that your baby would not have downs. Already you have been reading conflicting information on the net of either 1 in 100 or 1 in 1300.
A woman of 40 is usually only offer an amnio test if her results come back at 1 in 50 or less.
Get an appointment to see your midwife asap and then discuss your options further with her. Only an amnio will give you a yes or no result sadly and as you say, there are risks involved.