If it helps, FindMyPast have:
Title Records Cheshire Electoral Registers 3,784,694
Devon, Plymouth & West Devon Electoral Registers 1780-1973 74,093
England & Wales, Electoral Registers 1832-1932 5,499,028
England & Wales, Electoral Registers 1832-1932 5,538,072
England & Wales, Electoral Registers 1920 6,775,052
Hampshire, Portsmouth Electoral Registers 1835-1873 198,310
Leicestershire Electoral Registers 1836-1970 115,295
Manchester Electoral Registers 1832-1900 23,298
Norfolk Electoral Registers 1832-1915 4,557,906
Norfolk, Electoral Registers 1832-1915 161,799
Scotland, Linlithgowshire (West Lothian), Electoral Registers 1864-1931 23,469
Somerset Electoral Registers, 1832-1914 31,783
UK Electoral Registers 2002-2014 105,677,628
Wales, Monmouthshire Electoral Registers 1832-1889 54,032
Wales, Monmouthshire Electoral Registers 1832-1889 13,126
And Ancestry have:
Title RecordsAberdeen City and Former Counties of Aberdeenshire, Scotland, Electoral Registers, 1832-1976 3,219,223
Anglesey, Wales, Electoral Registers, 1832-1977 467,743
Bedfordshire, England, Electoral Registers, 1832-1986 17,982,277
Berkshire, England, Electoral Registers, 1840-1965 2,581,037
Bexley, Kent, England, Electoral Registers, 1734-1965 3,219,535
Cambridgeshire, England, Electoral Registers, Burgess Rolls and Poll Books, 1722-1966 1,694,140
Dorset, England, Electoral Registers, 1839-1922 1,584,958
Edinburgh, Scotland, Electoral Registers, 1832-1966 4,898,177
Fife, Scotland, Electoral Registers, 1914-1966 1,071,893
Fife, Scotland, Voters Lists, 1832-1894 47,875
Glasgow, Lanarkshire, Scotland, Electoral Registers, 1857-1962 30,247,020
Gloucestershire, England, Electoral Registers, 1832-1974 11,545,968
Liverpool, England, Electoral Registers, 1832-1970 8,128,468
London, England, Electoral Registers, 1832-1965 1 79,071,664
Midlands, England, Electoral Registers, 1832-1955 6,275,582
Newcastle upon Tyne, England, Electoral Registers, 1741-1974 10,239,239
Norfolk, England, Register of Electors, 1832-1915 4,481,061
Perth and Kinross, Scotland, Electoral Registers, 1832-1961 2,477,867
Surrey, England, Electoral Registers, 1832-1962 36,618,574
Sutton, Surrey, England, Electoral Registers, 1931-1970 3,823,328
Swansea and Surrounding Area, Wales, Electoral Registers, 1839-1966 5,918,713
UK, Electoral Registers, 2003-2010 65,219,200
UK, Poll Books and Electoral Registers, 1538-1893 4,677,818
West Yorkshire, England, Electoral Registers, 1840-1962 46,743,829
Of course, you need to read the detailed description of each record set to ascertain what exactly is included!