Commanderfish - A couple of questions if you wouldn't mind -
Tried to PM you but your inbox is full, so posting here:
1) My tailpipes are still original. I had them cut them off the old exhaust and welded onto new ones. You can't see the lines and the car looks stock. Or of course you can change to any number of new tailpipes they have in stock, but my advice is AR unwaiveringly get one thing right where most others are falible: styling. Plus, people don't know the car is modded. Remaps seem to be invisible and air filters are buried half an hours labour away.
2) Noise does increase, but it being a good solid engine, it sounds meaty rather than chav-corsa-loud-fart noise. It's important to explain to the fitters what you want, say you don't want it loud, you're just looking for power/torque gain. They'll understand. They actually dropped the bore of the exhaust on mine from 2.5" to 2.25", which increased back pressure and gave me loads more torque. They also replaced all the chambered boxes with straight through boxes which improved peak flow and power. It will be louder under load but not horrendous. Mine sounds like a meaty V6, I love it! It sounds more V6 than the stock V6 to be honest. Throttle response gets better too.
3) Warranty: Well yes it's going to void the warranty but only in relation to your old exhaust, which you will have thrown away! AR seem good at honouring the rest of the warranty from what I've heard, besides it's very hard for a manufacturer to argue that your new exhaust has caused problems to any other part of the car (okay maybe rear bumper paint-work if some monkey mounts the exhaust touching the paint, but seriously unlikely and you'd notice). Besides, the stainless steel exhausts from places like Torque Exhausts (Red Dot) come with a lifetime guarantee and are much longer lasting than the stock mild steel pile of pants that comes out of the factory (it's not just AR, all the manufacturers do that). So effectively it seems to me that you've got more warranty than before, since the original mild steel exhaust would probably have given up after the 3 year car warranty anyway!
3) Induction. Yes induction can produce a gain (and an even nicer sound) IF it's done right (it's pretty complicated from what I can tell, so personally I wouldn't install a "fits any model" kit like a Pipercross, because every car model has different airflow so you're probably just getting a nice noise for your money and you can even lose torque), but virtually no one has produced a kit for the Brera. I think Angel were going to do one but I haven't found any solid info on this.
As a start, you can get a sport air filter from Autodelta to replace your stock one, pricey at about £35 but improves the throttle response a bit (and still a very cheap mod in terms of actual spend). You need to put car on a little ramp and get the underguard off, or remove the right front wheel to fit it, but me and my dad did it on our own. Sport air filter won't give the gain you should get from a full induction kit if you can find one. I think I might do a new post on that actually.
Hope that helps!
Oh, and tell them you're coming from a long way away, tell them you want everything done on the same day so they book a big enough time slot and order in all the parts you need. For that reason you're probably better off getting it done on a weekday if possible, or first thing on a saturday at a push.