Hi,
The UTF-8 character set supports the UK currency sign. If the table and database are set to UTF-8, you can try entering the data directly into tables through SQLyog and check if it converts it to £.
I guess the data is being entered from somewhere else or where it is being fetched, there is some character set mismatch. Somewhere character set is ISO-8859-1 (most probably ) . If you are fetching the data on a HTML page, then check the encoding( content type ) in the head of the page or the content type in the header which the server is sending.