It is true. Being from the U.S., I found that the language use in the U.K. took some getting used to, as the controllers there use some local slang also, as do other English speaking country controllers. Things like "climb level three hundred" can be confusing at first. Made worse as in the U.S., many use the word "level" to mean "maintaining", whereas the rest of the World "level" pretty much ALWAYS means "Flight Level".
"Climb to flight level two eighty, radar heading 150, contact Brest control on one-two-eight-decimal-four-two-five-six-nine-five-trrrrreee standby callyouback."