LONDON, May 7 (Reuters) - Trading at the British publishing and exhibitions group United Business Media (UBM.L) has remained resilient and is broadly in line with expectations despite the "extremely challenging economic environment".

A UBM tradeshow

The company, which benefits from a diverse portfolio of trade magazines, trade fairs and print magazines, also announced on Thursday that Chief Financial Officer Nigel Wilson was stepping down to join Legal & General Group (LGEN.L).

Wilson, who spent seven years at UBM and was also deputy chief executive, will step down from the board immediately but will continue in the finance role until September.

UBM has transformed its portfolio during Wilson's time and the group said on Thursday its trading had remained resilient despite the volatile markets. It is also alert to the impact the swine flu disease could have.

The news sent shares in the group, which owns news distribution services such as the PR Newswire, down 2 percent to 475.5 pence at 1357 GMT, after an earlier flat trade.

UBM said it had a strong balance sheet and was increasing available liquidity which it thought was a key asset in the difficult credit markets.

Data and online services generated around 18 percent of overall profits in 2008 and are on track to deliver both a higher percentage and higher overall profits in 2009.

UBM's Events division contributed around 48 percent of the group's profits in 2008 and is on track to deliver a similar percentage of profits in 2009.

The exhibitors and sponsors, which generated around 90 percent of the revenue from events in 2008, continued to be in line with expectations and the group said it had good visibility in this area.

The biggest events, such as the Jewellery and Gem fair in Hong Kong, are also on track to deliver good growth.

UBM said, however, it had cancelled a small number of secondary events and expected a revenue shortfall of around 10 million pounds ($15.16 million) from technology events held mainly in the United States.

It said it was also keeping alert to the potential impact of a wider outbreak of swine flu. It holds no events in Mexico, the centre of the outbreak.

Print magazines, which are largely dependent on advertising, will contribute less than 10 percent of UBM's profits in 2009, the group said, as it manages its portfolio to mitigate the effects of the downturn and its long-term structural decline.

The Distribution, Monitoring and Targeting businesses have been boosted by client wins in the U.S. and are also on track to deliver a greater share of the 2009 profits than the 24 percent they delivered in 2008.

UBM said its balance sheet remained strong and said it had increased its long-term available liquidity by 150 million pounds through extending existing facilities and by arranging new facilities.

UBM will report interim results for the six months to June 30 on Friday, July 31. ($1=.6597 Pound) (Reporting by Kate Holton; editing by Rupert Winchester)