Here in Worcestershire, there is an organisation connected with the County Council that recycles cycles. and also uses spares etc.
As you mention Bristol and Penzance as possible dropping off points, I am not sure where you live. Under a search for "recycling bicycles" I found that Bath and North East Somerset Council, and North Dorset Council both have similar schemes for saving bicycles. There is also www.bristolcyclingcampaign.org.uk.
It might be worth you contacting your local council to see if they are doing something similar. I hope this is useful to you.