Bicycle Tutor

I have a Giant Escape n7 which has had the rear hub cleaned and a new bottom bracket to solve the problem of a grinding noise when pedaling. I think I may have it down to the chain rubbing on the front chain wheel/guard etc (whatever they are called) it is a 2007 model 7 speed. It is not the original KMC z41 chain that came with the bike, could th replacement chain be too wide, or how can i adjust the bike so the chain doesn't rub on the guard. any ideas? please help as I the shop is too far away to take the bike in and let them take care of it.
Regards
Wayne

Did the noise start when the new bottom bracket or chain was fitted? Support the bike so that you can turn the pedals and check the bike over for the source of the noise.
Turn the bike over and rest it on the saddle and bars if you have no way of doing it upright. Check the alignment of the back wheel to make sure it's central between the chainstays.
I suppose it's possible that the wrong bottom bracket has been fitted and the chainline is out?

Ok Thanks for that, I'll give it a try. Initially I made the mistake of taking it to Halfords and they fitted the new chain which on the receipt said bmx chain (looked too wide) they also used the wrong grease on the hub so when taking it to a shimano/giant specialist they had to special order in the bottom bracket but they felt the chain was ok. I shall try your recommendation and let you know.
Regards

BMX chain is 1/8" which is also the general width for single sprocket bikes including multispeed hubs.
3/32" is the standard for derailleur systems though I'm not sure about this now with the newer 10 & 11 speeds?
The chainline on single sprocket bikes should run straight from chainring to sprocket with no kinks.