It is the interior which has earned St Margaret's the name 'the Marble Church' from the variety of marbles used. The common interior stone is Talacre, but the dominant marbles are the red Griotte of the main chancel piers, which blends into the mature colour of the oak roof, and the Belgian Red of the nave arcades, which, perhaps intentionally, appears insipid by comparison.
The church is entered through a plain W porch, which leads by a double archway to the nave. At the centre are paired columns in Anglesey marble. The church is paved in Sicilian marble. In the porch the foundation stone, at left, has its inscription on a brass plate within a recess.
The nave consists of 5 bays of arcading, tall and narrow, with a 10-bay oak roof. The arcades are based on quatrefoil columns of Belgian Red marble with bulky foliage caps (carved by Henry Smith). These feature the rose, thistle, leek, shamrock and ivy. The roof principals rise above smaller Belgian Red marble shafts. Above the cornice at each side are 10 paired clerestory lights. These are separated by carved oak brackets supporting the feet of the arch-braces of the roof trusses. The spandrels between the arch-braces and the principals are pierced with foliations. The wallplates, the bearings of the trusses over the brackets and the collars are castellated. Light is admitted to the apex of the roof by 10 small staggered lucarnes each side. The aisle roofs are in 10 bays, with alternately braced and unbraced trusses, and with short green marble shafts at the principal positions carried on limestone corbels.
The chancel roof has large bosses (carved by Thomas Earp); roof principals with arch-braces with pierced foliation between, over Red Griotte columns with their colour heightened by contrast with bands and inserts of black Kilkenny marble. The chancel has wall canopies around 3 sides, those at E constituting the reredos, with Languedoc marble shafts and cusped nodding ogee heads of Caen stone and alabaster (carved by Harmer); at E the canopies have Povey marble inserted with painted inscriptions (the Lord''''s Prayer, the Ten Commandments and the Apostles'''' Creed).
The communion rails, choirstalls, pulpit (by Thomas Earp), lectern (1876, by T F Kendal of Warwick) and the pews are all in carved oak. The font (1862, by Peter Hollins of Birmingham - who also carved Lord Willoughby de Broke''''s tomb at Compton Verney) is in Carrara marble, featuring 2 nieces of Lady Margaret, who died young. The altar, reredos and communion rails of the War Memorial Chapel in the south aisle are in oak, to the design of W D Caröe, c1920. The pipe organ in the west gallery is by John Cowin of Liverpool. The bells are by the Whitechapel Foundry.
The middle windows of the chancel sides (c1880) are thought to be by Ward and Hughes; the others, including the E window and the W gallery window, are by O''''Connor, as are the 2 E windows of the aisles. Two windows at the W of the aisles (1881, 1896) and one adjacent on the N side (1910) are family windows by Ward and Hughes.