I agree with OG. It's not the best position next to a freezer. Given that, and also with the problem of getting the freezer out, the best option is to investigate an alternative position for the rad.
Perhaps replacing it with a smaller rad can be looked at. Maybe a 900mm rad, which would allow access to the freezer. That really wouldn't be a big job at all. Modern double panel rads are high output. I doubt if you would notice the difference.
You obviously have a cold external wall. In which case, heating in that area is a must. I would go for a shorter rad, but, it must be used, and not left turned down or off.
To the side of the freezer, I would fit a through-the-wall open vent to get some air circulation going. It's not ideal though, being open to the outside, but there really is no alternative with what is a cold, external wall.