Brunel University has a basic climbing wall in their sports centre, in Uxbridge. I'm not aware of any bouldering and there are no crags in the area. The nearest crags are the Southern Sandstone ones which are usually tope roped.
In reply to Pero: Avon is the quickest to get to from Uxbridge (apart from Southern Sandstone). About two hours by car. Swanage and the Wye Valley take a little longer.