I have no idea how long this fare will last, but Ryanair is currently offering return flights in April and May 2015 from London (Luton) to Copenhagen for a remarkable £1.98 all-in return (i.e. including taxes).
If this is of any use to you, be quick. It will not last long.
Here is an example booking we made just now:
Frankly if you only book this speculatively, the worst that can happen if you cannot go is you’re £1.98 down!