I haven't dusted the pc, yet, i'll do it on the weekend with my dads air compressor, but my CPU temp has slowly been increasing in temp over the last few months, i have a proper CPU cooler and thermal paste, what gives?
Given the difference in core temps, it is possible that you're not getting sufficient coverage of your thermal paste. It may be that your processor has bad contact between the cores and the heat spreader. If cleaning it doesn't work, try reapplying thermal paste.
Those do look a little high. I would suggest dusting/cleaning when you get the chance and checking temps after to see if it helps. If that doesn't work try replacing the thermal paste and making sure that the cooler is positioned correctly. For reference my Xeon is running at 27-31C at idle with the stock cooler. With a decent cooler I would think your i5 would probably idle around the same temperatures unless you have a significant overclock.