Online sales in the United Kingdom increased 18% in May compared with the same month in 2010, with consumer spending on clothes and alcohol helping to boost the totals, according to a report from the Interactive Media in Retail Group, an online retailing trade group, and Capgemini, a consultancy.

The groups’ monthly “E-Retail Sales Index” says that U.K. consumers spent 5.3 billion British pounds (US$8.5 billion) on online retail purchases last month, an average of 86 pounds (US$138) per person. The online spending figures include travel-related purchases; without that spending, the May e-commerce growth rate stood at 21.5%, the report says.

“Online is continuing to set the pace in retail, with both clothing and alcohol e-retailers performing particularly well in May,” says Tina Spooner, director of information at IMRG. “We are seeing a pretty clear split between the sectors selling low-cost products and those selling high-value ones, with travel, electricals and home and garden lagging some way behind in terms of growth. So although overall growth is very positive, it seems perhaps consumers are wary about making those big-ticket purchases in the current economic climate.”

Online liquor sales increased 25% in May compared with the previous year, and grew 5% from April 2011, the report says. An online consumer buying alcohol spent an average of 161 U.K. pounds (US$25) in May, the second highest average spending value since Nov. 2007; April’s average spending on alcohol was 174 pounds (US$280).

And with consumers apparently anticipating warmer weather, online apparel sales increased 24% year over year in May, the report adds.

By contrast, online travel purchases increased 12% year over year in May, and 13% from April 2011.