Not so much of where it is but more of how do I access it. I know its in the Tank but do I have to remove the Tank to get to it or is there access through the boot or from the back seat area?

Ok.
I got at the fuel pump and peered into the tank which looks quite clean inside.
However, i am going to remove the pump tomorrow. Before I do this, can anyone tell me what voltage it should be recieving from the ECU? I believe its variable whith engine speed.

Hi,just remove the tank centre unit,thats the pump and fuel gauge unit,and at the end of that is a filter,but have u tested the pump pressure,let me know what u done.cheers TERRY

I decided to pull off all the intake again today to check for air leaks and put in another set of Plugs despite the others only having done about 1500 miles. Everything went back together ok so I took it for a drive and its still the same. For some odd reason I decided to unplug the air flow sensor while the engine was running expecting it to stall. It didn't. It carried on as normal. I revved it expecting it to be uneven and lumpy. It didn't. I took it for a drive with it disconnected and the car ran like a dream. Perfect accelleration and idle. I plugged it back in and it was back to its old hesitant and misfireing self as you accelerate hard.
I have 3 of these sensors. Surely they all can't be dodgy. I'm just gonna dig out another one to try.

I don't really know what to try next in all honesty. If all 3 show the same problem then I think something isn't talking to something in the ECU.
Any suggestions anyone?

I swapped the MAF for one of my spares and it didn't make any difference. I swapped the K&N type panel air filter for an original type that I had lying around and guess what? The car is now running like a dream. I swapped back the MAF sensor and it still runs properly.
So, something has changed somewhere along the line. I used the K&N with my last Lexus and removed it before I sold it. I fitted it to this one not long after I bought it back in 05. I'm not convinced it was the cause all along but i'm gonna give the car a good ole thrashing in the next few days to see if it stays ok.

Hi ,well done m8 good job.nice to work on your own car,and fix it cheers TERRY

So far so good.
Car has had a good thrashing today and its still going really well and seems to have improved its fuel consumption although that could be psychological.
Its either that or its down to the new Oxy sensors.
Power delivery is very smooth and it comes in the way it should without any misfires or hesitancy right upto the red line.
Now I am gonna finally fit my 10 inch rears that have festered in the garage for the last 2 years, get it MOTd and thrash it within an inch of its life for the next 12 months.
Welcome back mate.

Nice one