I would suggest an Optoma HD67 from Richer Sounds for 399 pounds. I know its a little over your budget but I have been running an Optoma HD65 for the last 2 years and although its 720p and not full HD its a cracking little projector for the money and has a loyal following online. It introduced me to projection and I have near 1,500 hours on it now as does my father who has the same machine in his cinema room. I think it would eliminate any risk you may have in buying second hand and trust me, the picture is excellent for the price.