If you need information on how to lobby for improvements to cycling facilities, there are a number of organisations you might consider approaching.
The first place to try is Bricycles, a Brighton-and-Hove based community group that aims to make cycling easier, safer and more attractive in Brighton, Hove and Sussex. For more info go to http://bricycles.org.uk/.
For the Lewes area there is Cycle Lewes: http://www.cyclelewes.org.uk/
You may want to check what our local authorities are doing to promote cycling.
Brighton and Hove:
http://www.brighton-hove.gov.uk/content/parking-and-travel/travel-transport-and-road-safety/cycling
East Sussex:
http://www.eastsussex.gov.uk/leisureandtourism/countryside/cycling/default.htm
West Sussex:
https://www.westsussex.gov.uk/leisure-recreation-and-community/walking-horseriding-and-cycling-routes
East Sussex also has a Local Access Forum:
http://www.eastsussex.gov.uk/leisureandtourism/countryside/rightsofway/localaccessforum/download1.htm
Brighton & Hove Clarion Cycling Club 
Unfortunately on last checking, Bricycles, Brighton and Hove City Council and Sustrans do not seem to be doing much to make travel by ANY mode easier for residents and visitors.
I have personal experience of people that have said Brighton and Hove is now unwelcoming and will not be coming back to it.
There seems to be an inability to get a true picture of what people want by polarising all parties instead of listening to them objectively!
Some things have got a little better since you posted your comment. Valley Gardens, the seafront in Brighton and Madeira Drive are now much friendlier places for people to ride bicycles, to walk and wheel. The Council has also won funding from central government to improve cycling infrastructure along the coast road, from Hove Lawns to the lagoon, and along the main road from London past Preston Park. And work has already started to make the main shopping street, Western Road, better for cycling and walking. But yes, there is still a lot that needs to be done.