September 3rd 2015 (1)
September 10th 2015 (6)
September 17th 2015 (5)
September 24th 2015 (5)
There have been 17 by-elections for 18 seats during September 2015 with just one seat (5½%) changing hands. The results can be summarised by:
| Party | Candidates | Defended | Retained | Gained | Lost | Won | retention rate |
| Conservative | 17 | 8 | 8 | 8 | 100% | ||
| Labour | 15 | 6 | 6 | 1 | 7 | 100% | |
| Liberal Democrat | 13 | ||||||
| SNP | 3 | 3 | 3 | 3 | 100% | ||
| Plaid Cymru | 1 | ||||||
| UKIP * | 15 | ||||||
| Green | 9 | 1 | 1 | 0% | |||
| Independent ** | 5 | ||||||
| Health Concern | 1 | ||||||
| Left Unity | 1 | ||||||
| Libertarian | 1 | ||||||
| No Description | 1 | ||||||
| Richmondshire Independent | 1 | ||||||
| Socialist | 1 | ||||||
| Yorkshire First | 1 | ||||||
| TUSC / TUSAC | 2 | ||||||
| Total | 87 | 18 | 17 | 1 | 1 | 18 | 94% |
* Candidate in Caerphilly: Bedwas, Trethomas & Machen was disowned by party but remained UKIP on ballot paper
** 5 Independent candidates stood in 4 by-elections
The only seat to change hands was in a "double" election in Edinburgh: Leith Walk where the SNP candidate topped the poll, all parties having just 1 candidate
- Labour gained a seat from a Green although the Green share rose by 1.6% since 2012 with the Labour share falling by 7.6%.
Elsewhere Conservatives retained
- "marginal" seats at Maidstone: Fant (3% majority), Richmondshire: Richmond East (2%) and Wyre Forest: Blakebrook & South Habberley (23%)
- "safe" seats at Derbyshire: Derwent Valley (29%), Norfolk: Loddon (38%), South Cambridgeshire: Bourn (27%), South Norfolk: Chadgrave & Thurton (34%)
- but saw majority in Tunbridge Well: Southborough North fall to 4% on a 19% swing to Liberal Democrat since both May 2015 and 2014.
Labour retained generally safe seats
- Caerphilly: Bedwas etc (23%), Haringey: Noel Park (46%) & Woodside (41%), Wakefield: Pontefract North (24%), Sandwell: Blackheath (21%)
- although in Thurrock: West Thurrock & South Stifford (12% majority) swing to UKIP was ~3% since May with Conservatives not far behind in third.
SNP retained Edinburgh: Leith Walk and Midlothian: Midlothian West on swings from Labour much smaller than those in August
- whilst in South Ayrshire: Ayr East final majority over Conservative was 35 votes following Conservative ahead by 20 votes on first preferences
there was a ½% swing Conservative to SNP on first preferences.
Collated By MiddleEnglander
