BJ, an RCBO is simply a device that combines the functions of an RCD and an MCB in one neat package. They can be expensive compared to a simple MCB..£40 to £50 each, but they do provide total protection in the event of any type of fault occuring on the circuit.
A Two way enclosure, splah proof type, will be sufficient for your purposes.
Regardless fo the make of RCBO you Buy, I would suggest and MK enclosure, like this one (Part No: 5702s)
They look better than standard ones, but can withstand being in a kitchen without any undue influence from the environment they are in.
I would suggest a matched RCBO (Part No: 6932s)
I would further suggest that you do not buy these items from B&Q or any other shed, they will rob you blind, find your nearest Newey&Eyre or Edmundson Electrical, or similar dedicated wholesaler, you will save a significant amount on shed prices.