if I go to settings/network and then activate my personal hotspot, and attatch my iphone via usb and then connect to the internet using my phone as a modem, anyone know how this is charged by t-mobile or is it part of my allowance 600 minutes 500 texts and unlimited internet

It would come off your data allowance.

on most networks, tethering the device to a pc is against the fair use policy if there is unlimited data

I may be wrong but i think T-Mobile is one of the networks that allow tethering. I use tethering on my T-Mobile contract and have had no issues. My data plan is classed as Unlimited 1GB?!? which kinda contradicts itself but after 1GB usage I can browse and get emails but cannot stream or download anything until the new month.

Plus you should be able to connect a third party device (iPad, laptop) wirelessly using the hotspot. Well I can on my android phone

I'm on T-Mob and tether my iPad to my phone. Never had a problem and it's come out of my unlimited Internet.

Thanks all for the input, so it looks like for the last 2 years I've been wasting £12 + vat on a dongle for my laptop that I didn't need. Moral if the story never give a 62 yo old fart modern technology.
Again many thanks