Why am I not burning as many calories as before?

As you lose weight, you don't need as much energy to do the same movement. It's a good thing. But it's also why your caloric intake should decrease every 10 lbs lost or so.

The fitter you get, the less cals u burn as your body becomes more efficient .. sods law huh lol Which means, you have to work harder, faster or longer too xx

I think it is probably because you are getting more used to it and getting into better shape. It's a good thing!
Make sure you are using the HRM correctly (wetting the electrodes and strapping it tight, etc).
Kinda like how I used to DIE walking up a flight of stairs, sounding like a rhino, and now I don't

When i first began working out i burned a ton of calories. The more i workout the stronger my heart/fitness is getting so i burn less calories. I have to intentionally push myself harder or longer to get the calorie burn i used to get when i first started working out.

I know i was loving all the extra calories after 60 mins now i have to work twice as hard to get the same amount or more! LOL!

Something to consider: if your scale shows the same number but you know for fact your BF% is decreasing (like you're having a proper analysis done every so often or whatever), your energy needs go up. The part of your body that uses calories is your lean mass.

I purchased a HRM a few months ago and used it when I was playing squash. Initially for 60 mins I was burning over 1,000 calories. I have noticed recently that I am burning quite a few calories less in the same amount of time. I was wondering if it was a measure that my fitness was improving and that my heart was working less hard because it is fitter too. Advice anyone?

As you lose weight, you need to remember to adjust the setttings on your HRM to adjust for the new weight. I forgot to do this until I lost over 20 lbs. It does make a difference. But it is also true that your body becomes more efficient as you become more fit, as the previous poster mentioned.