Technically it does need to be fitted by a gas safe person. However it's dead easy of you get the right parts, they just push fit together.

Get it done

The main concern, and possibly the reason to have someone qualified look at it, is why do you need one fitted ?

If it's because the flue termination isn't sited correctly, then a Plume Management Kit won't solve that problem really.

There is still the air intake to consider, and that won't change.

Best to check the manufacturers instructions to see if your situation complies,then go from there.

Please consult a Gas Safe registered engineer, as there [u]are[/u] regulations as to where you can terminate a flue. There is also a maximum permitted flue length specified by the manufacturer.

Also the emissions may need adjusting on the boiler due to increased resistance on the flue (due to more bends & increased length) I certainly would.

Ben. Gas engineer.

Cheers - problem is at the moment it terminates in a narrow dead-end passageway about 3ft wide, facing the neighbours. so probably not brilliant siting to start with, and we've got plans for the passageway.

I was just asking because it seems easy to buy online, and it's hard to get definitive info on what needs to be done by a Gas Safe person and what doesn't.

It really all needs to be looked at/ discussed/ decided upon with a decent engineer who knows what they're doing.

Have a look on your boiler manufacturers website for approved engineers.