Yeahh, alot of people are really against it but as long as you know the HB may not be audible sometimes or can be difficult i dont see the problem..
I have another 2 scans to go, ive got my detailed 20 week/anomally scan and ive booked a 3/4d for 27 weeks.
I googled the angel sounds doppler in the shopping tab of google, some are only like £12 odds, free delivery on a couple sites which is really good!