The following Lat/Long values should be points of "easy access" for viewing Hadrian's Wall:
N 55Deg 0.133' W 1Deg 48.365'
N 55Deg 1.153 W 2Deg 3.643'
N 55Deg 2.207 W 2Deg 14.598'
N 54Deg 56.476' W 3Deg 11.833'
Note that one end of Hadrian's Wall ends at Wallsend, located just north of Newcastle.
Ordnance Survey grid refs:
MITHRAEUM TEMPLE NY 85900 71050
VINDOLANDA NY 77050 66350
HOUSESTEADS FORT NY 78950 68800
STEEL RIGG VIEWPOINT NY 75050 67600
CHESTERS ROMAN FORT NY 91200 70200
data from Usenet postings by Geoff A., Poul Bekker-Hansen and Neil Pugh.