Thanks to all. As usual, I know morenow than when I posted my question.

never, never exchange currency in the exchange booths, they are very deceptive in their advertising and some are dishonest to boot. ATM's are the best, if you must change notes go to a bank.

Never say never again. There are pretty decent rate exchange booths (2-3%) and there are others (scammers), as always. .
You did expect that in Prague, didn't you?

please feel free to name them please, that would be very helpful.

Chris, I do know how much I pay in fees! And some aren't that bad at all. Never is clearly wrong, just a few weeks ago at Pilsen station, the exchange rate was good. Please do name the "never never" places. That would help.

I was in several Exhcnage places a few weeks ago(just for research) and though they advertise great rates when you go in these rates only apply if you are changing over 50,000 czk crowns worth of currency,the other exchange rate for smaller amounts was about 20% less.
I use ATM's when travelling and even with bank charges find it is far the best rate going.

To give you a straight answer. If the business will accept euro, they will tell you. But take a look at the exchange rate you will receive.

Last summer I got a wad of local currency from the ATM at the airport and used that and my credit card for large purchases, e.g. hotel bill. Yes prices are quoted by hotels in euro, but I don't recommend trying to pay a cab driver in anything but koruna. For one, he cannot easily make change. For two, his meter is in koruna. For 3, he probably has no idea how to convert on the spot.
And for 4, he would probably be ticked off.

>> he would probably be ticked off.

You got that one right!

There are many money exchange offices around Prague. Some of them recently started to offer 0% commission. But look out for misleading rates being advertsied - often they quote the 'sell' rate (selling Czech crowns and receiving foreign currency), which is higher than the 'buy' rate you will get for selling foreign currency and buying Czech crowns.

It's reliable to change money in regular banks with a commission of 1.5-2% than paying an 8-10% commission to the exchange office or your hotel reception. A good one is Komercni banka with offices all around, easily recognizable by the red KB logo.

Credit cards are accepted in almost every hotel, store or restaurant. You can also use your card to withdraw cash from the many ATM machines around the city. UK Switch cards are not normally accepted.