When I first turn on my engine I get a weird grinding type noise sometimes. I've heard it happen on other 1.8t's but is it anything serious and should i be worried?

Do you mean the sound that the auxiliary air pump makes on first startup and first 90 seconds?, would say it was more of a "hoover" type sound than grinding though. If it is the noise you mean and it's quite loud, it could be that the pump rivets round the casing have started to break up - if so drill the rest out and replace them with nuts and bolts.

Not its doesn't sound like a hoover at all sounds like something gets grinded really briefly then stops just after turning the engine on

sounds like a sticky starter motor to me, does it only happen when cold? if its the starter it can usually be fixed by taking apart, re-greasing the cogs and putting it back on. or just replace with a genuine one. DONT buy a cheap one, you will regret it

Yep, it's a common noise. I bet most of the 1.8T's on this forum do it to a certain extent. I know mine does it quite badly. You can fix it like eggessford said by greasing the bendix gears on the starter, but it won't fix it for good. Only way to properly cure it is to get a new starter which is a revised design iirc.

Makes me look round when I hear the noise in a car park as you can tell it's a VAG.

+2 on the above - mine did the exact same.

Took the motor out, cleaned and greased, lasted about a month and then it came back so I just got a "new" one.

They are an exchange part from the dealers.

Are you having any problems starting the car when it is warm by chance??