LONDON (Reuters) - British consumer spending picked up last month, according to a survey from card company Visa UK that bucked other signs Britons have become more cautious since June, when they voted to leave the European Union.

Based on Visa credit and debit card usage data, consumer spending rose 1.6 percent in July compared with a year ago, up from June's 0.9 percent increase and the biggest rise in three months.

Seasonally-adjusted spending increased by 1.1 percent, the strongest month-on-month gain since January, reversing a 0.5 percent decline in June.

But the monthly data are volatile. Taken together, the last three months suggested consumers remain careful with their spending, Visa said.

"July's data suggests that UK consumer spending is holding up despite the ongoing uncertainty following the referendum, albeit at lower levels of growth than we've seen in the last couple of years," said Kevin Jenkins, Visa's managing director for Britain and Ireland.

Other research suggests consumer spending, a pillar of Britain's economy, has flagged since the Brexit vote.

Consumer confidence suffered its sharpest drop since March 1990 last month, according to a closely-watched gauge from market research company GfK.

Meanwhile British retailers reported the sharpest fall-off in sales in four years, though few major retailers have individually pointed to a big impact from June's referendum result.

Last week the Bank of England slashed its forecasts for household consumption, predicting growth would slow from 2.5 percent this year to just 1 percent in 2017 and 0.75 percent in 2018 as unemployment rises.

It cut British interest rates to a record low 0.25 percent and launched stimulus measures that could be worth up to 170 billion pounds ($222 billion).

($1 = 0.7653 pounds)

(Reporting by Andy Bruce; Editing by John Stonestreet)