The FTSE 100 was up 0.2 percent and the FTSE 250  was up marginally by 0836 GMT.

The pound's fall came after lawmakers wrested control of the parliamentary agenda from the government for a day in hopes of breaking a deadlock over Brexit and parliament will now hold indicative votes on a range of Brexit options on Wednesday.

International companies, which book a large amount of their earnings in the U.S. dollar, rose with pharmaceutical giant GlaxoSmithKline and Diageo, the world's biggest spirits company, leading the gains.

Ocado hit a life high on the main index with a near 4 percent rise after inking a partnership deal with Australia's Coles Group in its fifth major overseas deal in less than 18 months.

Housebuilders, considered to be exposed to an economic hit from Brexit, including Persimmon, Barratt, Berkeley and Taylor Wimpey rose between 1.2 percent and 3.1 percent after brokerage HSBC upgraded the stocks.

Traders also said parliament's vote to seize control of Brexit process could help the sector.

But Ferguson slid 9.2 percent and was on course for its worst day in three and a half years as the world's largest heating and plumbing equipment supplier said it expected trading profit for the year to be towards the lower end of analyst expectations.

Among the midcaps, housebuilder Crest Nicholson added 6.5 percent after naming Galliford Try's Peter Truscott as chief executive officer. Galliford's stock dipped 3 percent.

Medical devices maker ConvaTec surged 10 percent to its highest in a month after Swedish business daily Dagens Industri said several players are running the numbers on the company for a possible buyout.