The UK is electing 73 MEPs from across 12 regions - 11 have so far declared
The Brexit Party have 29 MEPs winning 32% of the vote and are largest party in nine regions
The Lib Dems have 16 MEPs, up 15, with a nationwide 20% share of the vote
Labour have 10 MEPs, down by 10, and their vote share has fallen to 14%
The Green Party have won seven MEPs, up four, with 12% vote share
The Conservatives have four MEPs, down 15, and are in fifth place on 9% of the vote
Change UK have not won any seats, nor have UKIP
In Scotland, the SNP have three MEPs, Brexit Party one, Lib Dems one and Conservatives one
The Brexit Party dominated in Wales, with Plaid Cymru second
Counting to determine the results in Northern Ireland began at 08:00
Overall turnout is 37%
In Britain, with 100 of 373 counts complete, the brand new Brexit Party is in the lead with 31.9%.
But it seems to have been a difficult election for the two largest parties, the Conservatives and Labour, who are down 12-14% each so far.
It's also been a good night for the pro-EU Liberal Democrats, which got just 6% of the vote in 2014 - and so far is on 12.5%.
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BBC Europe editor Katya Adler tweets...
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Change UK leader Heidi Allen says: It feels like there has been a big swing to Remain.
"People are not down-hearted - this is the beginning of something."
She says that the European elections "came too quickly" for Change UK to work with other Remain-supporting parties.
She adds that she hopes this will change before the next general election.
BBC political correspondent Nick Eardley tweets...
The final results from Scotland are yet to be announced.
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The Lib Dems vote share went up by 20%, and The Brexit Party by 18%.
Labour's share fell by 12.7%, while UKIP and the Conservatives fell by 14.8% and 14.6% respectively.
Labour's Emily Thornberry says: "We needed to be clearer and sharper and make it unequivocal about where we are going.
"The referendum result spoke to me an essential truth: Yes we leave the EU, but we need to look after jobs and the economy.
"That is what we have been trying to deliver against an intransigent prime minister."
Professor Sir John Curtice
Polling expert
Nothing illustrates more clearly the success of the Lib Dems in winning over Remain voters than the party's success at coming a clear first in the capital, something it has never come remotely close to achieving in a previous election.
The Greens have also prospered to some degree with a three point increase in its vote to 12%.
Meanwhile the Brexit Party have inevitably done less well here with a modest 18% of the vote.
Meanwhile the weakness of Change UK is underlined by its inability to get more than 5% in this most Remain party of England.
Brexit campaigner Suzanne Evans says: "It is quite interesting the Brexit Party have repeated UKIP's success from 2014.
"We have seen a clear switch from UKIP to The Brexit Party.
"I wonder if we are also seeing the death of two parties - the death of Change UK and the death of Brexit."
BBC political correspondent tweets...
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Laura Kuenssberg
BBC political editor
London is the beating heart of today's Labour party.
That is a very worrying result for them.
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Three Brexit Party MEPs have been elected in the East of England region.
The Lib Dems have had two candidates elected.
While the Greens and Conservatives each won their first seat so of the night - each seeing one MEP elected.
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The SNP's Alyn Smith Scotland says: "Taking the results in the round it is clear that Scotland is for Europe.
"That cannot be ignored.
"We need to see proper engagement with the voices in these islands to find a solution."
Professor Sir John Curtice
Polling expert
There are now some clear signs that Labour will come third in Wales behind not only the Brexit Party but also Plaid Cymru.
This will be easily its worst ever result in the country.
Professor Sir John Curtice
Polling expert
Here is a result that summarises the story of the night:
This is an election at which the parties of no deal and second referendum have clearly been much more attractive to voters.
Professor Sir John Curtice
Polling expert
On the basis of the results declared so far there is at least a 50% chance that the Lib Dems will come first ahead of Labour in London.
Lib Dem Sir Ed Davey says: "If you add up all the votes of the Remain parties, there is a strong message.
"The Lib Dems are leading that Remain vote and have an awful lot to be pleased about.
"We have to ensure that a no deal doesn't happen and that the people have the final say on Brexit.
"I think we're back in business."