Our brushless DC motor controller item number SPD-48600BLDC will replace the controller in the photo that you attached. The SPD-48600BLDC controller has more connectors than the Ryaca ES-020 controller has, however most of these connectors do not need to be plugged into anything and are there just in case they are needed.
I have identified every wire and connector on your old controller however I am not exactly sure what the connector with two blue wires goes to. It most likely goes to the brake switch I would imagine. Wherever it goes to the SPD-36600BLDC will have a connector to replace it. Here is a link to the SPD-36600BLDC controller's wiring directions: http://electricscooterparts.com/hookup/SPD-48600BLDC.pdf
The SPD-36600BLDC controller is available on this page: http://electricscooterparts.com/speedcontrollers48volt.html#48Vbrushlessmotor
Please let us know if you have any questions.
I do not know of any stores that sell this controller in the UK however we do ship our parts to the UK. Postage to the UK for this size of part will be fairly expensive though.
Please let us know if you have any questions.
Alex Black