Just an update on this. Purchased the pressurised bleeder and finally got around to changing the brake fluid three days ago. Also made sure to have the instructions for the bleeder and the brake bleeding procedure to hand. All in, it took me about two hours to do. A long time you may think, but I wanted to ensure that I was doing everything exactly right and wasn't going to be rushed. Going by the old brake fluid I disposed of, I also bled the lines a little longer than necessary, just to be sure, to be sure, to be sure! So thanks to all who helped.
BTW This is what happens when you're brain is scrambled and you want to change the brake fluid by yourself!
Could have done it just one wheel at a time!
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2001 A8 D2 FL 3.7 Q - LPG Conversion, Engine: AKC, Gearbox:FBB, Colour:LY5X Aqua Blue pearl effect, Interior:WJ light beige/dark beige valcona leather with burr walnut inserts
My DIY jobs -
Replaced alarm horn,
Replaced Coolant Temp sensor,
Updated RNS-D firmware,
Installed Reversing Camera and Digital TV,
Dashcam Installation,
Retrofitted Rear Blinds,
Auto-Dimming Rear View Mirror,
Chrome Boot Struts
Sold! 
2008 S8 D3 5.2 V10 - Engine: BSM, Gearbox:KLW, Colour:LY7F Suzuka Grey Pearl Effect, Interior:Black/Black with Silver/Black valcona leather with carbon atlas inserts, Bang & Olufsen, Heated windscreen, Soft-close doors, TV, DAB, AMI, Quad Zone, Auto Boot, Auto dim Mirrors, Keyless entry, PDC with rearview camera, AFS II Headlights
My DIY jobs -
Fan Jet Windscreen Washers,
Retrofitted Electric Side Blinds