You will find that members do not attempt valuations. If you are intending to put it on Ebay, for example, it is a relatively simple matter to search out all existing Whitefriars pwts and get a line on what is reasonable. If on the other hand your pwt is a rare one you would want to ask more. You can also have a look at the Whitefriars website where collectors of Whitefriars may be able to help you with more information as well.
I would advise you to be patient - you are likely to get lots more from other members here.