UK looking for sustained improvement after setbacks

The road towards a gender balanced House of Commons has been a long and slow one, but devolved parliaments were an opportunity for a fresh start for female representation in British politics. The first London Assembly in 2000 comprised 48% women, and in 2003 the Welsh Assembly became the first national elected body in the world to achieve gender parity among its members. The Scottish Parliament also saw close to 40% women in Holyrood in 2003.
These early successes proved to be a high water mark, however, and since 2003 the number of women elected to the devolved bodies has either stalled or fallen.

While more women may seek election and run for office, they are more likely to be contesting marginal seats and the increased number of candidates is unlikely to be reflected in the final tally of seats won:

However, indications are that the increase in female candidates may not translate into equivalent increases in women elected. In London and Wales the number of women elected is likely to be either stagnant, or increase by a very small amount. In Wales, the Electoral Reform Society Cymru recently published an in-depth exploration of the picture for the Welsh Assembly, and found that while all women shortlists and zipping are used – in particular by the Labour Party – women are significantly more likely than men to be defending “marginal” seats. Of the 11 battleground constituencies, ten are being defended by women.

https://theconversation.com/gender-balance-is-back-on-the-agenda-but-can-women-get-elected-in-2016-58829