Not got one in my sterling (yet), but in my old smaller pennine I just asked an electrician mate of mine to pop an extra 3 pin plug point in the storage under the bench seat. I then just cut rectangle hole in the front and plugged it in. It was only about £50 to buy.. Make sure it has a thermostat on it so it cuts in and out.. Also make sure nothing covers it in the cupboard! Pete
There are a few things to watch out for though. You may need to route out the cupboard opening a bit to fit the heater. Also the oven burner is sensitive to draughts underneath and the heater action tends to starve the oven of oxygen if it is on causing the flame to go out. The solution to this is to fit a divider behind the heater so its airflow does not affect the oven. In my case I retro-fitted a cardboard barrier sealed with duct tape and it cured the problem. Most people run the electrical connection into the socket on the right-hand side of the sink area. You need to make sure you don't overload the electrical system by limiting the heater to 2kw as Pennine do. I used the same Smiths SS2EW heater as Pennine factory fit.
Hi my OH fitted one , he is not electrical minded but he didnt have a problem. We got ours from B&Q . They where on offer for £23.50! came with remote control too! we love it and soon heats up the cabin!