I can't quite make it out, but looks like grey on some stems, if so that's blight, or it could be a shadow in the photo

The black ends could be "just" blossom end rot as suggested

Looks like blossom end rot. It's caused by the plants inability to uptake calcium. That could be due to a number of issues including irregular watering. I would cut off the damaged fruit. I use fish emulsion fertilizer and have perfect tomatoes all the time. That's what I would recommend.

is the brown area hard or soft to the touch? if hard it is blossom end rot and is due to insufficient water. this prevents the plant taking up enough claium ions. so remove them and water more often with a greater volume. with the fluctuation in temps in the uk it is a common problem this year.
if the toms are soft then it isn't blossom end rot but they are not showing symptoms of blight on the leaves, yet.

have a look at this link
https://www.rhs.org.uk/advice/profile?PID=217

If they're in pots, are the pots big enough?
It looks like late blight to me. Have you pruned off any leaves for better air circulation?
I think you may be in a losing rescue operation unfortunately. Snip off all affected fruit, remove all leaves from the bottom third, half the leaves from the middle third & any badly affected or yellowing leaves from the top. Then in a plant sprayer mix 1 litre of water, a teaspoon of bicarb or baking powder, teaspoon of vegetable oil and a couple of drips of washing up liquid. Shake well & completely cover the plant on a dry day.
There's brown marks that look like the branches have been damaged rubbing against something in the wind too which wouldn't help.
I'd make a few batches of spray & spray the cucumber too, different mould but thrives in similar conditions.
Next year after your toms are hardened off & settled in their outdoor spots spray them once a week for 3 weeks with 1 litre of water, quarter of a soluble aspirin & a drip of washing up liquid. The aspirin acts like a vaccine so that the toms develop better resistance to mould

I, like others considered Blossom End Rot and Blight but on second thoughts it might be Grey Mould and it would seem that some varieties are more susceptible than others. Have a look at RHS Tomato leaf mould on google for more info.

Thank you all for your advise and valued opinions.