Worcester Danesmoor 20/25 boiler water leak?

Boiler is about 5 years old, has just started leaking water, about 2 litres per day, have checked in and out connections on one side and blanking plugs on the other, they appear to be water tight.
It was serviced last week, is it possible they could have disturbed something?
Are there any other connections to check, have not taken side covers off, water is appearing from under boiler towards the rear.
Now need to top up system regularly so i know it coming from the boiler.
Is it likely to be the water jacket that's leaking?
Thanks in anticipitaion for any help or suggestions.
Ian