At one point, the FTSE 100 touched its highest level since August last year, reaching 6,757.96, but closed slightly off that, 26 points higher at 6,750.43.
ITV shares jumped 8% to 199.26p after its latest results.
It said advertising revenue was set to fall 1% in the first nine months of the year, which was less than feared.
Shares in housebuilder Taylor Wimpey rose 6% to 153.84p after it said it had not been affected by last month's Brexit vote.
Pre-tax profits for the first half of the year rose 12% to Â£267m, and the company said "current trading remains in line with normal seasonal patterns".
"Customer interest continues to be high, with a good level of visitors both to our developments and to our website," said chief executive Pete Redfern.
Sentiment in the market was helped by the release of stronger-than-expected UK growth figures.
The UK economy grew by 0.6% in the second quarter of the year, according to official figures, faster than the rate of 0.4% in the previous quarter.
However, the data suggested growth was much stronger in April before easing off in May and June.
On the currency markets, the pound fell 0.27% against the dollar to $1.3095 and dropped 0.28% against the euro to â‚¬1.19230.
(Close): London's main share index rose on Wednesday, helped by better-than-expected results from ITV and strong UK growth data.