Japan Tobacco to raise UK prices by 10p-12p a pack

* Plans price rises for Nov. 24

* Price of a 20-pack to go up by 10-12 pence

* Increases British market share

* Mayfair brand becomes Britain's top seller

LONDON, Nov 11 (Reuters) - Japan Tobacco (2914.T) is to take advantage of the growing popularity of its British cigarette brands, such as number one seller Mayfair, by raising the price of a 20-pack by 10-12 pence from Nov. 24.

"The momentum is with us, the wind is behind us, and we should harvest that," UK managing director of JT International Daniel Torras told reporters on Wednesday, adding higher tobacco leaf costs were behind the price rises.

The maker of Benson & Hedges and Silk Cut cigarettes in Britain said market share gains had prompted it to go ahead with price rises of nearly 3 percent now, as it looks to take the lead on pricing from arch-rival Imperial Tobacco (IMT.L).

"Our goal is to be number one in the UK and we expect to close the gap over the next few years," Torras said.