Invisage: forgive me for butting in. Company Refs gives the average PEs on which shares have traded over the last 5 years, and I think that information is interesting and useful.
However, Jim (and we) are looking for 'something new' (management, product or process) that will give an extra growth spurt and may justify a rerating to a higher prospective PE, so if you think you have found that you need to make allowances accordingly.
Don't forget also the risk factors Jim mentions: cash flow, gearing and so on (and a new one now, the pension deficit). Beyond certain limits, any of these can enormously increase the potential downside, so that the risk may not be worth taking.