I answered your question in relation to Anglo-Saxon England here. The essential answer is yes, there was almost certainly a system of signal beacons in place to warn against attacks along the English coast, and my thesis works on showing that there was a similar system in place along the inland border with the Danelaw too. We also know from contemporary accounts that the Carolingian Francians made use of an inland beacon system against a Lotharingian invasion.

In late Anglo-Saxon England, watch stations would most likely have been manned by small detachments of the fyrd militia. In many cases, the hilltop sites are located above, or within a couple of kilometers of a settlement, so it's quite likely there were rotating shifts. At sites like Totterdown in Bristol, the toponym tot-earn-dun means 'watch-house hill' so it's likely that there may have been a permanent presence on the site itself, whereas at sites like Beacon Hill in Stafford, the watching mound is a short walk above the Anglo-Saxon settlement.

The discovery in Mercia of sherds of Stafford Ware - a tenth century pottery produced at Stafford seemingly solely for the use of the Mercian fyrd - at several tot and weard sites suggests that the watchmen assigned to them were stationed there from a nearby garrison force as dedicated spotters rather than just a local manning the site whenever he had the time.