You have to bear in mind that B&Q usually sell cheap and that goes for the
installation service too.

They employ anyone who wants the job and don't pay a lot of money either.

So, you'll probably end up with a rough job.

Better to go to a proper specialist fire company. Look out for one who has a
nice neat shop without all the fancy stuff that you will end up paying for.

I had a power flue fitted recently by a local shop and the job was superb.