An  friend of mine had big problems with a porter in a building she was living and working in so I would really warn against it.

Most of the porters were ok ( everyone had to sign in so they all soon clicked on!) but one guy started getting a bit over friendly and thought he was at liberty to just drop by her flat  when he felt like it. When his advances were rebuffed he starting demanding payment and when she refused, the building management people somehow found out she was an escort.

It was pretty embarrassing as they called her to the office and they had found her on the Internet and printed out a page to show her  and asked her to hand in her notice 

I suppose you never know when people can turn on you and you don't want someone having that kind of leverage over you.

But there may be other people who have had different experiences so it is worth hearing what others have to say too. Good luck flat hunting x

well i wouldnt  put my money into renting a flat that has a porter  or conceirge or anything remotly like that but thats just me  if it were just for a few days then maybe but not full time   
also in ported block things can easlily change  management wise in that  you could move in and then in three months they start having to sign in all the guest ect   
you could easlily lose a couple of grand if you get it wrong  like the other post mentioned  you could easliy be asked to leave and you could lose your deposit as well   

Thanks for all the advice. Looked at a portered block today and they had a sign in book so won't be choosing that flat. I saw another flat in a large house. It would be sharing a front door but all the flats are self contained and the rooms are not close together. Any advice on renting a flat if you have to share a front door. I know it is a bit risky but probably better than a portered block. There is no video entry phone, but I can buzz people into the corridor, then let them in my door. I am not sure if it is ideal really.  

I have corrected the error! oops