It will certainly show you are keen, but in my opinion it wont get you any further up the queue.
There are plenty of people with un-validated ATCO licenses from private colleges kicking around at the moment that you are unlikely to get taken on with a view to paying for your training as well.
The best route in remains NATS - its tough and I know right now there is a bit of a back log but the demand is there long term. The best thing you can do is get as much exposure to the industry and get some knowledge about air traffic so when you can apply it will help you get through the selection process .
I think you would be better off getting some aviation insight - can you get a job at an airfield doing anything, is there a flying or gliding club near you where you can help out for free in exchange for a few passenger flights with a headset on or experience in the tower with a FISO.
Without jobs out there, the course you mention sounds like a waste of £1000 to me.