tomatoes outside under cloche?

About the furthest point from the coast in England, and that's where my frost pocket, outskirts of village plot is, as far as you can get from warm coastal temps, in my village it's generally 2 to 3 deg C below overnight temps in the local town, and very often it's another 2 degrees lower outside the village. I've had -3 deg C there in the 1st week June.

And I can't rely upon forecasts, the other night's forecast was 6 deg and it was - 0.6, last nights forecast was 3 deg and it was 6 deg, although temps in the tunnel I monitored were not much higher, despite leaving it shut all day to warm things up.

Last night in tunnel, 6 deg outside, not much warmer inside

Yes, and check what your min temps are and don't rely on weather forecasts that can be for nearest town/city with higher overnight temps.