Diesel Performance Box Chip

hello all,
need some advise please, I have a RR TD6 on a 55 plate and done 150000 miles and has a full service history, I brought her last year and is the best family car we have ever owned we have had shoguns in the pass but the RR is in another league, anyway in the year of owning her I've spent about £2500 on repairs one was a major service had everything done and fixed and the other was my own fault I had it remapped to give her better fuel economy and I bet the more experienced of you guessed what happened next........yes the gear box gave up, anyway a long story short it was the torque pack convertor luckily no damage to the gear box but had to have it rebuilt and a new convertor fitted.
My question to all you experienced owners and mechanics is the mpg is about 18-19 miles I knew when I bought it that it wouldn't be great but I have seen on the web about these performance box chips and what I have read could return me 30mpg or more the one I have seen is £80 on ebay and you can set the switching to give you more bhp and torque or fuel economy or both has anyone heard of these boxes and are they worth getting but my main worry is do you think that it would put extra strain on the gear box/torque convertor as I just cannot afford another hefty bill. I am not after anymore power just want better fuel economy.
Sorry about the long winded thread but I am desperate to find a solution and before anyone says we drive the RR like we're driving miss daisy lol thanks for any help in advance.

Mel

More torque, more power equals more fuel use that's the way it is. Should do a round 20-25 MPG, wear lighter shoes. Chipped on along steady speed motorway run you may gain a bit better consumption because of the more linear mapping.

As above. If a lot of your driving is around town then it'll never do much. Get it on an A road or motorway and it should do the figures you quote. I can get 600 miles to a tank on a run. Round town I get about 200 miles to a tank! Well, maybe 300. Not much more.

Wammers is again spot on. It's how you drive it. if you want a racing car, then get one.
Range rovers are not made to be driven. They're made to take you places. You're mean't to drive them like the queen is sitting in the back.

To get good economy, read the road. You don't want to be accelerating & then braking. Coast it before you start applying brakes.
I personally wouldn't chip or map the ecu. The gearbox's on those L322's are not the strongest at the best of times, & although the engine can take it, the gearbox will start complaining.
Besides that, there's nothing worst than watching a range rover getting thrown about or racing off up the road. It make's it look like a chav has nicked it.
Katie price parked her range rover next to mine once. I sold mine that very week.