Kraken, Coinbase are the most popular options. There are some other ones that works in the UK only I believe, like CoinCorner but it's not as big as the two previous ones.
I suggest you read their FAQ, etc. before doing anything to make sure the withdrawal time and used payment methods suits you.
Binance doesn't operates in UK?
I have came across few people asking similar questions and Binance wasn't listed to them, meanwhile within my locality here It our Number trusted exchange even p2p has trade gas been disabled yet we still have lot of people using it to trade maybe after they finished and want some Cash they do transfer to other exchange that allows p2p trade to do their fiat trading.
Since Binance was sued by the US government, they have also had a lot of trouble with the European market. Some countries have revoked licenses, some have banned them...so Binance is no longer a name mentioned much or a popular choice for investors, instead Coinbase and Kraken are more popular choices.
Binance is now more active in Asia, Africa, and Latin America. So, if you are from these regions, it is no surprise that Binance is considered the top and most popular choice.
What is more interesting is that despite the difficulties that the US and Europe have caused Binance, they still hold the top position in the market and account for more than 50% of the market's trading volume. So, it would be remiss if we didn't mention Binance when talking about top trusted exchanges.
This September, Binance also hit a major milestone when it became the first exchange to process over 100 trillion cryptocurrency transactions, double the capitalization of the US stock market.
https://cryptoslate.com/binance-leads-the-pack-with-100-trillion-in-all-time-trade-volume/