The difference in demographic spread in medieval times as opposed to now is clearest in the NW of England. None of the large conurbations of Lancashire existed in medieval times. There was a small see at Carlisle, where the Augustinian priory became the cathedral in the C12, but Cumbria was poor and sparsely populated. Chester was a reasonably important port with a thriving trade with Galicia, so it's entirely possible that pilgrims to Santiago also enshipped here. It also had a pilgrimage to the shrine of St Werburgh, now reconstructed at the E end of what was the Benedictine abbey of St Werburgh and is now the cathedral. The Norman church of St John's was briefly the cathedral (secular canons) in the C11, but nothing remains of the Benedictine nunnery, or the 3 friaries.
Further N, the small priory at Birkenhead, a daughter of St Werburgh's, was dedicated to St James, and the priory's seal depicted St James as pilgrim. As it controlled the ferry over the Mersey, it's possible that pilgrims to Santiago passed this way, but more numerous will have been the pilgrims to Chester and especially Holywell (see my pages on N Wales). The chapter-house is still used as a church, and various other parts remain, incongruously set in the remains of Birkenhead's shipbuilding yards.
From Chester, a Roman road ran SE to Whitchurch and Wroxeter, and for modern walkers the Marches and Shropshire Ways roughly follow it. E of Shrewsbury are the remains of Augustinian Haughmond Abbey, and in Shrewsbury itself, the Benedictine Abbey became a pilgrim destination when the relics of St Winefride of Holywell were brought there in the C12. There is still a fragment of this, plus a modern commemorative window.
From Shrewsbury, the Severn Way will take you SE to Wroxeter, where the church retains Saxon parts and was a collegiate church in Anglo-Saxon times, and the next monastic remains, that of Cistercian Buildwas (see also here). And from here it is only a short walk to the considerable remains of the Cluniac priory at Much Wenlock, which became a shrine with the relics of St Milburga (photos here).
From here, pilgrims could have continued on along the Severn to Worcester, but we will turn towards Hereford and head SW along Wenlock Edge, where the obvious route is the Shropshire Way. To the N at Church Preen, the exceptionally narrow chapel is the descendant of a small cell of Wenlock priory and the churchyard is celebrated for its ancient yew, which may be 1500 years old. Further SW, Cardington has a medieval church of St James, as does partly-Norman Shipton on the other side of Wenlock Edge.
The bridleway leading down from Wenlock Edge to the village of Munslow over Munslow Deans and marked by a line of yew trees is also known as Pilgrims Way, and probably marks the pilgrim route from Much Wenlock priory to Ludlow and the shrine of Thomas Cantilupe at Hereford (the road along Corve Dale is known as the Apostles' Way).
W of Ludlow, and N of the village of Wigmore, are the remains of Augustinian Wigmore priory, now called Abbey (see Cult of St James page). Both this and the current church in the village were/are dedicated to St James; there is a plan of the abbey on the Historic Herefordshire site. From here, continue to Leominster, where the church is what remains of the Benedictine priory, a daughter foundation of Reading abbey. The Marches Way can then take you S to Hereford.
Hereford cathedral (secular canons) housed the shrines of 2 saints: Ethelbert, an Anglian king (to whom the building is still dedicated), and the C13 bishop Thomas Cantilupe. Besides the cathedral, remains of the Dominican friary can be seen, incorporated in the Coningsby Hospital, a Hospitaller foundation, part of which is now St John's Medieval Museum with displays on the Templars and Knights Hospitaller.
S of Hereford at Aconbury was a nunnery, originally Hospitaller, later Augustinian, though little remains of it; nearby is St Ann's Well. Near Goodrich, the remains of Flanesford priory are incorporated in a farmhouse, now holiday accommodation. Then follow the Wye valley, perhaps using the Wye Valley Walk, via Monmouth, where parts of the Benedictine priory survive, notably the oriel window now called "Geoffrey's Window", and Tintern, one of the best-known and most picturesque of Cistercian abbey ruins. Just N of Chepstow on a hill in a bend of the river is Lancaut, where are the ruins of the medieval church of St James. Chepstow too has remnants of a Benedictine priory, in the parish church of St Mary.
Cross the Severn bridge, which replaced a ferry, and the Severn Way will take you into the centre of Bristol.