Two households self isolating meeting up?

Sorry.
Most of us have obeyed the 'rules' to the letter, and many of us are in the same situation as you! You are not unique.
My son and family live just down the road and have been strictly self isolating, so if I follow your reasoning we could visit. BUT my son's wife's parents who also live down the road have also been self isolating too ---- so which set of grandparents are allowed to visit?
I also have a daughter with a family who have been strict about self isolating - can I visit her too? She also has another set of grandparents (her in laws) so she should visit them?
If we all visit our respective isolated households what happens to the rules then? How many people has that mixed together?
If your rules apply and we've all been really careful about isolation - why can't we have a party? After all, we've all been self isolating.
No - it just doesn't work like that.
There are enough people already in hospital - think about the extra work you will cause them when you're admitted, and think of the family member who could well die from an infection you could have given them. Just because you are in isolation doesn't mean you can't catch it, you handle your groceries that many others have handled .... the virus can linger .....

From the briefing today, there was no sign of the guidelines ( which are in place to save lives) being relaxed.

I really find it hard to credit that after nearly 6 weeks of lockdown, people are still justifying breaking the rules or at least “bending” them.
It is us “oldies” who have most to lose if we get Covid19, but all ages can catch it and there have sadly been fatalities among children as well as young adults.
The short answer to your question OP is “No, it is not OK”
Is that clear enough?
Can you really not wait just a little longer until restrictions are eased?
In WWII the population faced years of bombing, followed by years of rationing, and also months and years of being separated by their children when they were evacuated.
Is another couple of weeks too much to ask?

Nanatoone Are you (and anybody else in your house) totally self-isolating, apart from seeing your grandchildren? If both their parents are key workers, there's a chance they could become infected. The children could also be infected, although maybe asymptomatic. They could infect you and if you're going out shopping, there's a chance you could infect other people, who could then go on to infect others … and so it goes on.

It is against the guidelines, as is looking after your grandchildren key workers or not one of their parents should be caring for them. I’m hoping the rules are relaxed very soon, can’t wait to see my grandchildren .

There’s nothing to say except it’s against the guidelines as is your behaviour Nana - never mind, do what you want, individual choices as to how to behave during a pandemic is absolutely fine as you are clearly so much more entitled than the rest of us.

I take the view that you need to risk assess what you are thinking of (you seem to have done this) then act appropriately. I still see my grandchildren, I've always looked after them and its much less risky for me to look after them than one go to school (five year old) and the baby go to a childminder who is also a carer, parents are both key workers. It's much safer for them to be with me than with strangers at school or a nursery. I can't see how what your are thinking of is dangerous, especially if none of you are in vulnerable categories. I'm pretty these rules will be relaxed next week anyway. By the way someone reported a friend whose birthday it is, as his family members came round and dropped pressies off and chatted, all at the social distancing norm. The nosy neighbour called the police saying they were having a party! This has made us a nation of nosey neighbours (well some of us), the police officer was annoyed at having their time wasted and spoiling my friend's lockdown birthday.

How have you all be getting food and other groceries?

How will you buy fuel for the car, if needed?

Have none of you been accepting post?

It may be something that will be relaxed, but at the moment it’s a no.

But it is true it is against the rules.

In theory it sounds ok but I wouldn't be sure about putting it into practice!

It is tricky isn’t it? My DS had his SiL round at Easter as she was lonely and they had all been self isolating for a number of weeks. Personally I do not see the problem but if everybody did it it was cause problems as not everyone would be as careful as you.

It is against the current rules to mix two households.