57 plate Mondeo mk4 1.8tdci.

Will engine remapping help performance and fuel economy. My usual garage has just invested in the equipment

And wondered if it was worth doing.

Yes it will help performance and likely improve economy as long as you stick to the way you're driving now, you might end up putting your foot down more because it's more fun, depending on the price it's worth doing

Yes as you have a turbo engine it will make a difference you can have it remapped to get better performance or economy or a bit of both.I know my engine is totally different and you won't get these gains but the first map I had increased the BHP by 50 BHP so went from 225 to 275 ( I did also have the inlet and  full exhaust 200 cell cat as well) but even without the mods  and standard kit it still would have improved a lot. I did go a bit further and had it moded to 340BHP( about as far as you can go with out forgeing the engine silly money then)  With your  Turbo diesel you will gain a lot of new Torque and you will notice that a lot go ahead and do it I honestly think you will like the results.