Thank you to MiddleEnglander for collating this information.
There are a further 26 local council by-elections identfied during the rest of July. So far another 10 have been called in August, 8 being in Scotland, together with a double election already in September. In addition there are a further 16 known vacancies and impending vacancies, 9 in England, 5 in Scotland and 2 in Wales. Currently 19 of the total 61 contests and vacancies occuring since the general election are as a result of the resignations of the sitting councillors as they are now MPs.
9th July - 8
East Sussex CC, Old Hastings & Tressal - Labour died - 5 candidates: Con, Lab, LD, UKIP, Green
Gwynedd UA, Morfa Nefyn - Plaid Cymru resigned (now MP for Dwyfor Meirionnydd) - 2 candidates: Plaid Cymru, Llais Gwynedd
Hastings BC, Central St Leonards - Labour died - 6 candidates: Con, Lab, LD, UKIP, Green, Ind
Hastings BC, St Helens - Conservative resigned - 5 candidates: Con, Lab, LD, UKIP, Green
Houslow LB, Brentford - Labour resigned (now MP for Brentford & Isleworth) - 5 candidates: Con, Lab, LD, UKIP, Green
Hyndburn BC, Spring Hill - Labour died -4 candidates: Con, Lab, UKIP, Green
North Lanarkshire UA, Thorniewood - SNP resigned - 7 candidates: Con, Lab, SNP, UKIP, Green, Socialist, Christian
Sandwell MB, Newton - Labour resigned - 4 candidates: Con, Lab, UKIP, Green
16th July - 8
Cumbria CC, Greystoke & Hesket - Conservative resigned - 2 candidates: Con, LD
Denbighshire UA, Prestatyn East - Conservative resigned (now MP for Vale of Clwyd) - 4 Candidates: Con, Lab, UKIP, Ind
Kingston-upon-Thames LB, Grove - Liberal Democrat died - 5 candidates: Con, Lab, LD, UKIP, Green
Norfolk CC, Gorleston St Andrew - UKIP disqualified - 5 candidates: Con, Lab, LD, UKIP, Green
Norfolk CC, Mile Cross - Labour resigned - 5 candidates: Con, Lab, LD, UKIP, Green
Rother DC, Battle Town - Conservative resigned - 4 candidates: Con, Lab, LD, UKIP
Tendring DC, Rush Green - UKIP resigned - 4 candidates: Con, Lab, UKIP, Ind
Wrexham UA, Llay - Labour died - 6 candidates: Con, Lab, LD, UKIP, Ind., No Description
23rd July - 5
Blackburn with Darwen UA, Mill Hill - Labour resigned - 4 candidates: Con, Lab, LD, UKIP
Caerphilly UA, New Trdegar - Labour resigned (now MP for Merthyr Tydfil & Rhymney) - 3 candidates: Con, Lab, UKIP
Elmbridge BC, Long Ditton - Liberal Democrat resigned - 4 candidates: Con, LD, UKIP, Green
North East Lincolnshire UA, Croft Baker - Labour died - 6 candidates: Con, Lab, LD, UKIP, Green, TUSAC
Westminster LB, Harrow Road - Labour resigned - 3 candidates: Con, Lab, UKIP
30th July - 5
Aberdeen UA, Hilton / Woodside / Stockethill - SNP resigned (now MP for Aberdeen North) - 5 candidates: Con, Lab, LD, SNP, Green
Aberdeen UA, Kincorth / Nigg / Cove - SNP resigned (now MP for Aberdeen South) - 5 candidates: Con, Lab, LD, SNP, Green
North Kesteven DC, North Hykeham Mill - Lincolnshire Independent resigned
Northumberland UA, College - Labour died
Wychavon DC, Droitwich East - Conservative died
6th August - 5
Glasgow UA, Anderston / City - SNP resigned (now MP for West Dunbartonshire)
Glasgow UA, Calton - SNP resigned (now MP for Glasgow Central)
Glasgow UA, Craigton - SNP resigned
Glasgow UA, Langside - Green resigned
South Lanarkshire UA, Hamilton South - SNP resigned (now MP for Lanark & Hamilton East)
13th August - 3
Falkirk UA, Denney & Banknock - SNP resigned (now MP for Falkirk)
North Lanarkshire UA, Wishaw - SNP resigned (now MP for Motherwell & Wishaw)
Powys UA, Glasbury - Conservative resigned (now MP for Brecon & Radnorshire)
18th August - 1
Orkney UA, West Mainland - No Description died
20th August - 1
West Oxfordshire DC, Witney North - Conservative sitting as Independent resigned
10th September - 2
Edinburgh UA, Leith Walk - SNP resigned (now MP for Edinburgh North & Leith) and Green resigned
Known vacancies in England - 9
Barnsley MB, Dearne North - Labour died 23rd May
Cornwall UA, Camborne Pendarves - UKIP resigned around 10th June
Derbyshire CC, Derwent Valley - Conservative died 5th May
Durham UA, Shotton & South Hetton - Labour died 23rd May
Norfolk CC, Loddon - Conservative died 23rd June
Peterborough UA, West - Conservative resigned around 10th April
Sandwell MB, Blackheath - Labour died 15th June
South Norfolk DC, Chedgrave & Thurton - Conservative died 23rd June
Tunbridge Wells BC, Southborough North - Conservative died 29th May
Known vacancies in Scotland - 5
Aberdeen UA, George Street / Harbour - SNP impending resignation
Aberdeen UA, Midstocket / Rosemount - Conservative impending resignation
Fife UA, Glenrothes West & Kinglassie - SNP resigned as now MP for Glenrothes
Midlothian UA, Midlothian West - SNP resigned as now MP for Midlothian
South Ayrshire UA, Ayr East - SNP resigned as now MP for Ayr, Carrick & Cumnock
Known vacancies in Wales - 2
Caerphilly UA, Bedwas, Trethomas & Machen - Labour died 7th May
Caerphilly UA, Cross Keys - Labour resigned 14th May