I make it probably eleven tunnels of varying lengths on the various sections of line used by XC between Wolverhampton and Southampton Central (via Oxford).
New Street North tunnel (751 yards) and Arena tunnel (176 yards) between Smethwick Rolfe Street and Birmingham New Street stations.
New Street South tunnel (254 yards) just after leaving Birmingham New Street.
Beechwood tunnel (300 yards) between Berkswell and Tile Hill stations on the section (between Birmingham International and Coventry).
Harbury tunnel (between Leamington Spa and Banbury) is 70 yards.
Litchfield tunnel (between Basingstoke and Micheldever) is 198 yards.
Popham No. 1 tunnel is 265 yards and Popham No. 2 tunnel is 199 yards. (Also located between Basingstoke and Micheldever).
Wallers Ash tunnel (between Micheldever and Winchester) is 501 yards.
St Cross tunnel (between Winchester and Shawford) is 62 yards.
Southampton tunnel (between St Denys and Southampton Central) is 528 yards.
Hope that helps but possible I've missed a few.