Corona virus has made me realise how little I have to give up.

[ssd]

No holidays I had been looking forward to, no festivals or shows to go to, no weekends away, no large gatherings, no family get togethers as they're all dead.
Being skint and lonely has its advantages in these times.

Pretty much the same here, OP

Same here! I’m about 10 years ahead of everyone else with self isolation.

I don't know whether to be sad or happy

Happy at the moment but sad when this is all over which it will hopefully be by summertime. Then why not resolve to organise some exciting things for the future like you have listed. I plan to take my own advice here too!
Plus they don't have to be expensive things but make plans to have fun nonetheless.

I have ME so feel like I have been rehearsing for self isolation for the last few years!

Ditto!

Turkey, I can't think of much that doesn't involve needing spare money. And when this is all over, me and dh will probably have been off work with very little pay, ds's both uni students with part time jobs they may lose due to this and rent still needing paid.

Fun involves money.

I'm sorry things are so difficult money wise. But fun doesn't necessarily involve money. It depends what you call fun.
I've just done a quick Google and found these ideas, I bet there are loads more much better free things too.

• Go on a picnic (in the better weather obvs).
• Go to no-costmuseum and zoo days.
• Local free music events.
• A potluck dinner party.Host a dinner party and ask everyone to bring a dish to share. If you are not comfortable with cooking, maybe try and learn how to cook a new dish together with your friends.
• Host a spa day.Give each other manicures. Try out new hairstyles. Make some facial masks or exfoliates using natural, at-home ingredients.
• Movie marathon.Log into Netflix and watch every episode of “Stranger Things” Or do an ’80s movie marathon, watching “Pretty in Pink,” “The Breakfast Club” and all of our old favorites. Don’t have a Netflix membership? Get the free trial just for the marathon!
• Book clubs

As I say I bet there are loads of much better ideas than this but don't give up on the idea of fun because money is tight. What are your interests, could you join some free social clubs with DH when things settle down, meet new people do something different?

I could try
Thanks so much for your suggestions that's very kind of you

it's made me realise how few social contacts I have (!)
On a social-closeness scale of 0 (lone hermit on remote island) to 100 (never alone 24/7, multiple carers), I think I'm about a 22.