I would go for a fixed VHF as the performance is much better than a handheld, and a simple hand held GPS (my preference is something like a Garmin 12). A hand held GPS has the bonus of being able to do your route planning in the pub, rather than sitting in the boat in the rain trying to enter waypoints!
Cheap plotters aren't really a whole lot of use, as the displays are too small. A depth sounder doesn't come into my list of essentials if you are on a tight budget.
You could get something like a Simrad/Navico Axis Fixed Waterproof VHF for under £250, plus about £40 for an antenna, and and a Garmin 12 for about £100.
for good prices!