Am i able to log into my account at a diferent address at the same time if there was a good football match on as a example?
Yep, this is possible where you can watch two streams on your nowtv account from different addresses in the UK.
If you are allowing a family member or friend to use your account on their device, then you must trust them fully with your account information.
I would also recommend that you add a payment pin to you account to avoid them buying unwanted extra passes on your account.
You can add a four digit security payment pin by going to My Account > Settings & Pin's whilst signed in on here.