UPDATE

Campercraft replaced the radiator and all was fine til a week ago. I've had it back a month and here's what's happened.
When I picked up the Bongo I noticed that the coolant alarm was staying on longer than usual when started up. Bill noticed it too, but said Bongo was running great.
As he said, the bongo ran great. I did notice the coolant alarm was staying on for way longer when first started up in the morning, way longer than usual. Once warmed up the coolant alarm was like normal. Start engine, quick 1-2 sec beep and off.
I had a look at the level of the coolant and it was below full when cold, I read up on it here and it said it should be full when cold so I topped up with water, about 400ml. The level is still full now.
A week ago I started to notice the bongo wasn't driving smooth, thought it was me. And, I also just put new 17 inch alloys on and thought that might be making it feel a wee bit rough.
Yesterday I noticed a lack in power, not a lot but definitely not as quick if I put my foot down, I also smelt a burning rubber smell when I got home.
Today a friend and I jumped in the Bongo to see what he thought. We drove to North Berwick and back, about 25 miles, we definitely both agreed that something was not right, it also felt like it was going to cut out while idling at lights. Got home and as we got out the bongo we could both smell a burning rubber smell from behind the passenger seat.
Also, we couldn't get the heater to blow through the front window to de fog it, nothing coming out of it at all.
Called Campercraft and told Bill the symptoms and he said it doesn't sound good, (Cylinder Head

)
The bongo isn't over heating or losing coolant. I have another alarm, I think an engine alarm, it never gets above 82. will post photos of both alarms.
What do you think?