Wen, who was to hold talks with the British leader in London, also vowed to support the crisis-hit eurozone, noting it was in both parties' interest to keep the bloc afloat.
The premier on Sunday told the BBC that "we will welcome more British products into the Chinese market" during the second day of his three-day British visit.
On the first leg of his three-nation European tour, Wen promised officials in Hungary that China would continue to support its faltering economy, and pledged to similarly aid the eurozone.
"We reached agreement on the Chinese government buying a certain amount of government debts," he said.
"That is China lending a helping hand to Hungary at a time when that country is in difficulty," he added. "We have done this for Hungary and we will do the same thing for other European countries."
British Culture Secretary Jeremy Hunt spelled out the increasing importance of the Sino-British relationship, calling the Asian nation an "incredibly important economic power and a massive investor in the UK".
During Monday's leaders' summit, Cameron was expected to tell Wen that British companies would be more inclined to do business with China if its human rights record was improved, according to The Times newspaper.
The pair were set to announce deals worth over £1 billion ($1.6 billion, 1.1 billion euros), according to British media, including a lucrative agreement for British company Seamwell International to develop clean coal technology in China.
Wen on Sunday toured Britain as Beijing freed dissident activist Hu Jia in a move seen as defusing tensions over human rights.
Wen arrived in the central English city of Birmingham on Saturday, while news emerged that Hu, one of China's most prominent prisoners of conscience, was to be released.
Hu, 37, was jailed on subversion charges in April 2008 after angering the ruling Communist Party through years of bold campaigning for civil rights, the environment and AIDS sufferers. His release followed that of outspoken Chinese artist Ai Weiwei last week.
On his first full day in Britain, Wen launched the first new MG car to be made in 15 years, the MG6 model, hailing it as a potent symbol of friendship between London and Beijing.
The new MG6 will be assembled at the MG car plant in Longbridge, Birmingham, which is now owned by Shanghai Automotive Industry Corp (SAIC), China's largest automaker.
"The successful cooperation of the production of the MG6 and other MG vehicles is a symbol of the friendship between China and the UK," said Wen, speaking at Longbridge.
"The model can be summed up as designed in the UK, manufactured in China and assembled in the UK, thereby making the most of China's capital and markets, as well as the UK's technology and managerial expertise."
The Chinese premier later held separate meetings with former British leaders Gordon Brown and Tony Blair and vowed that support to Britain and Europe would be "in concrete actions," according to China's state run news agency Xinhua.
Wen was keen to deepen China's "exchanges and cooperation with Britain and Europe", adding it was in the "fundamental interests" of both parties and vital for world peace and stability, Xinhua said.
Wen leaves Britain for Germany later Monday.
Meanwhile, Chinese dissident Hu returned home earlier Sunday after completing a jail term for subversion -- but seemed likely to be muzzled anew.
Britain's Foreign Office has yet to give an official reaction to Hu's release.
EU foreign affairs chief Catherine Ashton welcomed the news -- but her spokesman stressed the bloc's demands for Beijing to treat Hu fairly and accord him "full rights" after his release.
Germany said it will press human rights issues at its first joint cabinet meeting with China later this week, including the conditions of Ai's release, Foreign Minister Guido Westerwelle said.
Earlier on Sunday, Wen indulged his interest in Shakespeare with a visit to the bard's birthplace in Stratford-upon-Avon, where he was treated to performances of extracts from the play "Hamlet".