Bollix69
A couple of things to be wary of, make sure the GPS doesn't have a max speed limit, heard there were some out there that stopped at 100kts which is probably fine if all you do is fly a tiger moth or a C150 and use flap for descent
The other thing is the voltage that the unit will allow, some with the ciggy plug will only have a couple of volt tollerance around 12v which is not much use as lots/perhaps most aircraft are using a 28v system.
You can save yourself some money by not getting a specific aviation hand held with the disadvantage being it won't have an aviation database in it and you will have to put them all in your self. I got a Garmin 12 XL volt range between as I recall 10-40v and I got it working through the window of a BAE146 so no speed limit problems either. I didn't mind entering my own data base but thats a personal thing. Also think about an external antenna, can be handy to put that up on the dash and have the unit on the seat or somewhere rather than having the unit on the dash in the sun all the time (LCD screen didn't love it) and having to pick it up every time I wanted to check it. Not all units have external antenna options so its worth being aware of it.
My Garmin 12 XL is a great robust user friendly unit, if your looking at them though watch out for the plain Garmin 12 though as it has no option for external antenna and very limited voltage (at least that was the case a few years ago, could well have changed)