No, it's ludicrous. Apples and oranges. One is capital deposits by a third party which may be withdrawn at any time, the other is an annual production figure. The true comparison would be annual British profits from the deposits and annual profits from our output, if you could construct such a figure.. In any case, GDP is a very dodgy measure, being a guesstimate based on relatively few data. It includes construction for example, completely different in nature from manufacturing output.
You might as well say that Russian deposits dwarf the amount spent on healthcare or any other random measure you want.
The weight of Russian balances could be compared to total uk balances, but that would not be as good political propaganda.
https://tradingeconomics.com/united-kingdom/banks-balance-sheet#:~:text=Banks Balance Sheet in the United Kingdom averaged 3775841.04 GBP,Million in September of 2014.