It will depend on your height above sea level (and Shoreham tower's).
VHF radio range is very simple: it won't normally go over the horizon. The radio horizon in miles is roughly 1.3 times the square root of your height in feet. Add your horizon and his, and if they are less than the distance between you, you're not going to hear him.
If Shoreham is 20 miles away, you'll need to have your aerial about 240 feet high. If you're on a 250 foot hill, with falling ground towards Shoreham, you'll be OK. Check the OS map for heights - I don't know the area well.