We have a 1yr old Jack Russell bitch - Crumble.
Friendly but not overly confident.
Recall is not too bad when we are on our own but if there are other dogs, distractions around we are not interesting enough.
She will run up  to anyone/any dog, barking. She won't go right up and cause a problem but it's not acceptable behaviour.
If we see the person/dog we will put her back on the lead.
She has been well socialised - puppy training classes, dog play centre.
She is nervous when walking in town.
I do carry a bag of treats and a squeaker.

We have one other JR who totally ignores dogs, people etc and until he went deaf had brilliant recall.
He Mum is a bit similar in character but her dad isn't.

Any ideas on how to progress?

It sounds like you have not practiced training (sit, wait, stay, recall etc) with distractions. Therefore she has no attention span when distractions occur because she has no experience with dealing with them.

She is only 1 years old, and she has already learnt key skills so progressing shouldn't be too hard as long as you are patient!

Remember that dogs like to play and have fun, we humans are always insisting they are on best behaviour We want our dogs to be sociable, but to come when called when they're having fun meeting new canine friends. It's such a contradiction to a dogs simple mind.

I think Crumble will blossom into a lovely little JRT :)

Thank you, I will start doing that :)