The award was announced at this year's GBBF today (Tuesday 8 August), held at London's Olympia.
Head brewer Karl Graves told The Morning Advertiser: "I have got butterflies in my stomach.
"Every brewery would like to win it and we have been close before."
'Won't sink in'
He added: "It won't sink in for a few days yet.
"[My first thought was] I had better get brewing some more Goat's Milk!
"Everyone deserves this because everyone works hard."
Paul Hamblett, brewery sales manager, told event organiser, the Campaign for Real Ale (CAMRA), on accepting the award: "Goat's Milk is our biggest selling beer – it's a nicely balanced beer with a hoppy edge.
"We originally brewed and named it for a festival taking place in the Goat pub, and the beer just caught on. It's the first time we've won the competition, and we expect it to put us on the map."
Great British Beer Festival
The award follows almost a year of local tasting panels and regional heats, allowing the best beers from across the UK to compete at the GBBF.
Final judging for the competition was held at the GBBF, where more than 50,000 people are expected to sample from more than 900 beers, ciders, perries and fine wines.
Of the overall winning beer, CAMRA national director responsible for the competition Nick Boley said: "Congratulations to Church End for winning the Champion Beer of Britain award for Goat's Milk, which is the highest beer accolade in the country.
"Goat's Milk is a stand-out beer – it has a lovely balance of malts and hops, and a full flavour. It is a very fine example of a bitter and [is] incredibly refreshing."
Society of Independent Brewers (SIBA) chief executive Mike Benner said: "It is wonderful to see a SIBA member brewery once again winning the Champion Beer of Britain top prize.
"This comes as proof that the best beers in the UK are being made by independent craft brewers such as Church End, which should be hugely proud of its achievement.
"It was obviously a hit with judges and I'm very much looking forward to trying it very soon."
Maggs' Magnificent Mild
Good Old Boy
Afghan Pale Ale
Red Bull Terrier
Black Port Porter
Champion Winter Beer Winners
Old Ales/Strong Milds
Grainstore - Rutland Beast
Sulwath - Black Galloway
Magic Rock - Dark Arts
Barley wines/Strong Old Ales
Moor - Old Freddy Walker