Linesider, you're right to question that 'HD ready' rubbish. At least the PCworld chap did the right thing and point you to a forum
That Optoma is 800x800, ie not 4:3 aspect (not widescreen) and not 'HD ready' by any stretch of the imagination. High Definition comes in two flavours - 720x1280 pixels or 1920x1080 (aka 'full HD'). Projectors broadly fall into 2 camps, bright, usually 4:3 aspect data projectors, designed for presentations in rooms with some ambient light, and 16:9 aspect home cinema projectors, which are better in darkened rooms.
Home cinema projectors will give you a higher resolution (720 lines at your target price), widescreen aspect, and a better contrast ratio. Data projectors are normally MUCH brighter, but lower contrast, and 1024x768 4:3 resolution. This doesn't stop you using it for movies, or widescreen video from a camcorder - it's just not optimised for it.
My advice would be to phone Ken at Ivojo
http://www.ivojo.co.uk
I got both my office data projector, and my home cinema projector from them, and their advice is second to none. They have a superb range of all flavours of projector, so will give you impartial advice. (They're also normally one of the cheapest places around).