Find out the cost of the management company if there is one. Speak to them directly if need be rather than get misleading info from estate agents.
Check out parking (if needed) and area re safety, amenities, transport etc. If possible, would recommend exploring the area at night, as late as possible, and possibly even at 3am on a Sat/Sun to see if there's a lot of noisy people staggering home from the pub! Call local police station to see if they are able to give out any info on area safety.
If you're buying large furniture, check if your postcode is accepted for delivery. Currys won't deliver to a friend's flat cos their van once got attacked whilst making a delivery (few small things nicked, not like a baseball bat attack!), even though it's not a bad area. Their loss of business, but worth checking that at least one company will deliver your fridge! Unless you have a van and strong people to carry things 
Most importantly, check out neighbours. Especially at night, if you can, re music/parties/elephants playing basketball. This goes for both above/below, and side neighbours. If poss, pop up/down to see neighbours before buying - bit nosy, but say if you work office hours, having student neighbours who party til 3am during the week can be a nightmare... Equally a lovely old person who watches TV all night at top volume because they're deaf and insomniac... or someone who works offshore but parties solidly for the two weeks they're at home... Also check the door security works, buzzers, CCTV etc.
Also worth knowing if neighbouring flats are owned or rented re potentially constantly changing neighbours, empty flats (which seem prone to springing leaks!), dodgy landlords...