I've nearly completed one. But, I wouldn't do an RS3 Conversion on a £1500 car. By the sounds of that price, it's either damaged, acquired cheap through a PX deal, got spaceship mileage or its a CAT D/C. You're going to end up spending £3000 or more on parts, inc steering wheel and DRL's. Then labour will cost you anywhere from £500-£1500 depending on how much you do yourself. Your old parts will be worthless unless its an S Line, and then selling it for a profit or even for your cost price will be a headache.
You mentioned, just changing the grill. Well, to change the grill to an RS3 one, means you have to change the bumper to an S3/RS3 bumper, which means you have to change the headlights for the bumper to fit, change the front panel for the headlights to fit, change the wings for the bumper and headlights to fit, which means you have to change the bonnet for it all to work. Then you will have to change the side mirrors to LED ones, so that the car passes it's MOT because it needs side repeaters. Then it will look like it's sitting too high, so you will spend another £100+ on springs. Then it will still look too high, so you will want to put side skirts and 19"s on it. But then the rear of the car will look like a bog standard A3, so you'll have to buy a rear bumper, or if it's an S line one, just the Valance and diffuser. Then the RS3 rear spoiler and brake light.
Then the Rear Led lights with adaptors, or make your own adaptors. Then the Exhaust. On top of that, adaptors and coding for the headlights.
Not trying to put you off, because I actually want you to do a conversion. It's a good experience. However, don't do it on a standard a3 with no extras. And I'd recommend you to do it on a DSG model, as that's what RS3's come in.
If you need any more help or advice, please ask me. I will help you as much as I can, as I've recently done one, so now is the best time to ask. Thanks
