Very impressive and enjoyable. One point about the battle site which isn't shown on your historical map is just how hilly it is. The Castle Inn stood at just about the top of a very significant slope running all the way down to the river Ver - when you drive up (up Holywell Hill, which is actually pronounced locally Hollywell Hill) you wonder whether your handbrake will hold the car if you need to stop. There's also a slope running down to the east from the site of the Castle Inn - much shorter but steep - steep enough for a fat old man like myself to get out of breath when climbing up while carrying shopping.
It is an interesting little part of Hertfordshire. In addition to the Cathedral there's also the site of John Churchill's home (Holywell House) and the workplace of Samuel Ryder (remembered through the Ryder Cup).