Investing in Budapest District XIII: Gateway Properties called the Atrium

Pesti Hazak is indeed the developer, but to have a good guess on the quality of the work you should know the construction company.

I know the existing Vaskapu & Maxima projects of Pesti Hazak, and in general Pesti Hazak seems to deliver basic construction work & finishes. Nothing more, nothing less.

So long as it not finished to a lesser standard! These apartments are not high class top of the range apartments, but not low class either (i hope), so as long as the buidings are finished to an acceptable standard without too many glitches then I will be happy.

Is there a similar/comparable UK firm that you could describe them alongside?

I'm not from the UK, so I don't have a reference.

In general the (recent) construction quality in BP is quite deceiving. You really need to be careful at hand-over, and make a complete list of the items that need to be repaired.
Of course there are construction errors that you will only see / experience only after a little while. That's what the 2 yr guarantee is for. The workers of the construction company are obliged to come back until everything is fixed at your satisfaction.