David, don't forget an armour-plated, padded pocket for your specs mate!
Have a look at Deerhunter - they do a range of waterproof kit. Mine has been tested in very heavy rain. Thin enough to ware over layers, with a hood and waterPROOF.
Weihrauch HW100KT .177
Weihrauch HW98 V-Mach .177
Weihrauch HW80K .22
Weihrauch HW77K .177
Weihrauch HW45 "Silver Star" .177
Weihrauch HW35 .177
Daystate Mk.4 Panther .177
Air Arms FTP900 .177
Glevum Target & Sports Club, Gloucester.
Parkstone Gun Club, Poole