Yes it is a case of sending it back to the shop mate.
The fact of the matter is, and loads of replies will come back regarding trying this and that as we all need to show we 'know what we're on about', but with PCP's it's really hard to pin point an issue with the mechanics due to the lack of them. If there is an issue deep internally, it won't be worth the effort doing it yourself as another issue may be caused.
However, if it's a simple thing, such as value, firing pin, pressure etc then read the replies and act as you will. If I was you, it would be back to the shop. You've only had