I have to agree with this. I drive from London along A2/M2 to Sittingbourne way and often temp falls by anywhhere from 2-5oC on the hot days but never as much as 10oC unless of course there are factors like fog. I'd say 32/33 London and 30/31 for most of north Kent sounds spot on to me
Also seen this...London to feel like 40oC on Wednesday ...ouch