There is a pre paid rank outside the hotel and are very safe not dodgy at all. We used them last year. Its manic but def not dodgy and the prices are all displayed on a board. Its just like a cab office here.

ah, thats cool, thanks for putting our minds at rest Any idea how much it would be to Calungute/Baga? we're just trying to roughly work out how many ££s we need to take with us! Thanks

Less than £10

Make sure you go to the prepaid taxi counter outside the airport. There is one inside and it is expensive.
You will need rupees so change about £20 inside the airport. Haggle about the exchange rate as the one displayed is for about £1000 not £20. There are 3 or 4 booths so you can shop around.
Cost to Candolim last season was 650rps, Baga is probably 100rps more.