be careful not to touch that capacitor for a while after you unplug the unit as you can get a buzz from the power stored in it,this discharges itself after a while.....there are a lot of companies in the UK that make nice transformers, can you get a photo of that sticker on the top and put it on here ? and I will look out your best solution and tell you where to look at/order from online...
A new one of that size will probably cost you about £30.00 and about £8.00 for delivery due to the weight(probably about 9Kg)
I can post you some connectors,heatshrink, clips and a few lengths of wire for when you do the change/replacement (for free-I have lots of spares)as you will need them when you cut the old ones off....
The square black coloured component on the bottom of the case stuck down with the bolt going through it(with a heatsink/radiator) is a Bridge rectifier and rectifies (flattens out) the 24Volts AC(Alternating current) that comes from the step down transformer...and makes it 24Volts DC (Direct Current-just like the power from a battery)
Any questions just ask as I am on here regularly...