The blue chip FTSE 100 <.FTSE> index was down 0.6 percent at 6,954.22 points by the close, but up 0.8 percent for October.

Shares in WPP (>> WPP PLC) rose 4 percent and posted their biggest daily gain in four months. WPP, the world's largest advertising group, reported results in line with expectations.

"We are encouraged by the positive nature of this morning’s update and remain fundamentally positive on WPP’s ability to capitalise on a solid medium-term outlook for global advertising spend," Roddy Davidson, an analyst at Shore Capital Markets, said in a note.

However, investors were less optimistic about some forthcoming earnings. The top fallers were Shire (>> Shire PLC), which reports results on Tuesday, and Next (>> NEXT plc), whose results are due on Wednesday, down 2.8 percent and 3.2 percent respectively.

The FTSE 100 index posted a fifth month of gains in a row for the first time since early 2013. The index has been buoyed by a rally in banks and mining companies.

Banks were boosted by last week's well-received earnings from Barclays (>> Barclays PLC) and Lloyds (>> Lloyds Banking Group PLC), with the FTSE 350 banking sector <.FTNMX8350> hitting its highest level for the year.

October saw the FTSE 100 set a record high of 7,129.83 points. A weaker pound has bolstered the index, which has rallied about 10 percent since Britain voted in June to leave the European Union. The cheaper pound helps the index's international, dollar-earning firms.

Some analysts, however, were more cautious on the outlook for British shares.

"(The FTSE) is still continuing the positive run of gains since Brexit, so it's a Brexit bounce. But it's run into that previous record high ... and pulled back quite significantly from there," said Jasper Lawler, market analyst at CMC Markets.

Investors, he added, were holding back before upcoming central bank interest rate decisions and the U.S. presidential election on Nov. 8.

"I think no one's really got the confidence to buy the market up through into new record highs."

The more domestically exposed FTSE 250 index <.FTMC> fell 0.6 percent, and was down 1.8 percent for the month of October. It has been weighed down by a spate of profit warnings and big declines from companies including Berendsen (>> Berendsen PLC), Cobham (>> Cobham plc), Senior (>> Senior plc) and Keller (>> Keller Group plc).

(Editing by Mark Heinrich)

By Kit Rees and Alistair Smout