Where are you in the UK - that makes a big difference, and how long have you had the vine? And are you growing this vine outdoors in the ground out in the open, or planted outdoors with the growth under glass, in a south facing position, or growing it some other way?

I suspect the soil/lightlevels and water are all different and that's why they don't do as well.

We're in Northampton and it is just planted in the garden. It's planted against a fence and is relatively sheltered by the large trees in the forest behind. The garden gets sun in the afternoon (but not so much in the morning). It's been in the ground for about three years.

Is there something that I can do to help it? It seems to be thriving as a plant, but not so much as an edible fruit producer.

Are you growing the same variety as th ones in your other garden? Worth checking which varieties are hardier in GB?

Ah, now there's a question :) Unfortunately, the house in Bulgaria had the vines planted when we bought the house. It was an estate sale so I have no idea what variety they are. The ones in the UK I have no idea about either. I've had a search through my mailbox and can't find the confirmation email from the order. I realise this doesn't make it any easier for anyone to help me :) so general advice is probably the best I'm hoping for.

Should I give it more water? Should I try some lights to help it? ANy other general good advice I could try?

Sorry, I've never grown one - never trusted the climate! But I seem to remember that some of the UK hardy ones do indeed have small unappealing fruit. Best grown in a glasshouse here in many parts of the country(You didn't put your county on your profile)

I think you may get some help from http://www.brynnevineyard.com/ which is at Brixworth,. not too far from you