I think its called Polonia. I think they do a wider selection of East European cuisine than just Polish.

Is it worth a visit?

If you like vodka - most Polish restarants keep an incredible range of excellent vodka. Including some you might not have come across before.

It looked very busy and buzzing when I passed it on the bus last night (sat 30th)

I went on Friday night, my bloke's family are Polish. Very nice indeed, but they are unlicensed until the 9th May so take your own drink. When we went, they asked us what we wanted in Polish and then in English, it was great.
I had vegetable soup as a starter, and it was like chicken soup with a whole carrot, peas and potatoes in it, gorgeous. Then I had battered pork, they bring the mash and roast pots out on a big plate just to pick it.
Well worth a visit, it suprised me how many people actually came in for menus whilst we were there. They're also opening a shop next door that sells Polish jewellry and ornaments etc.

I'e been to the Polish restaurant in Oxford and the food was really good, though I can't remember what I had - probably because the vodka was also very good, especially the one that tasted like I was drinking a christmas cake :-) I'll definitely give this one a try now I know it's there.