Do I need a stronger wheel?

I'd get a stiffer rim, if the wheel you have constantly needs retruing. Also, if the wheel is perfectly true to start with, it is far less likely to go out of true.

Thanks, mate. Suggestions on stiffer rims that aren't exorbitantly expensive?

The guys at the shop checked the wheels before I bought them and they were pretty much spot on so I don't think it was bodgy to start with.