Hi there. unfortunately its not really how exploring works, people spend a long time building up locations so its unlikely anyone will just hand them out.
best place to start is searching this &/or other forums using key works like town names / county etc.
Geograph is a handy site, this you can search for key words like "abandoned" then a area, this will give you pics & location but some of them are very old so its a bit of a gamble.
The best way is often good old google maps, just spend some time scouring them to see if anything catches your eye.
I dont know bognor area at all but am guessing there will be plenty of old sea defences down that way that may be worth a look & would be easy for your friend.
Thanks for your message, yeah a know what you mean some urbexers dont and some dont care iv been doing exploring over a year now some places i will tell if someone asks depending on what it is ect, i know portsmouth is not far from there andd could places there also.