I have enjoyed creating a pleasant cycle route from Dieppe to Paris, which many people are using, often as part of a London to Paris cycle challenge. I'm providing this for free, but if you have done and liked this challenge, why not make a donation to Sustrans, the National Cycle Network in the UK?
I have been involved as a volunteer for Sustrans in Guildford, where I live. I've been able to allocate some of the funding I've raised for Sustrans to small projects in our area, such as making a special sign in a local park promoting routes from Guildford (from where you can cycle traffic-free to the coast via a disused railway - a good start for Guildford to Paris!). So a small donation can help make more people aware of all the wonderful opportunities to appreciate our countryside by bike.