The Liquid guidelines is and international standard for international flights and in some places also domestic flights. In Australia you are allowed liquids which are not things like acid, lighter fluid and other very highly flammable things in your carry on baggage for domestic flights but the moment you go for an international flight the liquids have to be in a ziplock bag and no more than 100ml per container and I think it is up to 1L worth. They can be ridiculously fussy. I had a liquid paper pen in a plastic bag wrapped around many many times to make it so it couldn't leak in my bag. It wasn't ziplocked though. Because the plastic bag didn't have the ziplock on a flight from Hilo (Big Island in Hawaii) to Honolulu (Oahu Hawaii) they refused to let me through security without disposing of the pen or putting it in my checked in baggage!!! I'd travelled to 4 continents and about 20 countries with that pen in my bag with no problems until that time!
I'd put your liquids in your checkin baggage and get other things which would most likely weigh more out. If you have stuff like a large bottle of shampoo which might add half a kilograam on to the baggage weight but isn't too pricey to replace, if your baggage is overweight chuck that out. Wrap a jumper around your waste if it is T-Shirt weather, wear your heaviest clothes, put some books in your carryon baggage if you have any. Stuff like that will hopefully get your baggage down a bit. If you are returning to the UK maybe even wear two layers of clothes because it will be quite cold and that would reduce the baggage weight even more. Pack heavier items which are not going to get confiscated through security in your carry on bag and hopefully they don't weigh it (only do this if you have a small bag because larger bags do usually get weighed and then you'd have to put it in checkin baggage).