Yeah I had a similar experience - Ap51 direct from Germany, Mk IV from Hak5 took a month to arrive what really gripped me about the duty tho - the duty was calculated at approx £3 however the Royal Mail put a £9 handling charge on the duty!!!!
I have bought a PCB hornet from Crucialwifi without issue, really quick delivery and cheap shipping - the supplier refunded excess postage costs to my PayPal account! But the flashing process isn't as straightforward on the Mk IV as the mark III - I have found the parts at fairly lo-cost on EBay to flash. The other point with the PCB it doesn't have the familiar SMA connector for the antennae instead using a (ipx ?) connector more common with 3G dongles. So if you have existing antennas you may need a suitable 'pigtail' to interface.