Coffeebean, if you have any other tips can you please share them here?
Well, if you insist...
For Tallinn I would browse through
http://www.select-a-room.com/ or a similar site. You can search for the nights you plan on spending, and you'll get a list of hotels and room prices. I had a look at Baltic Holidays, and to be honest, their prices seem quite inflated. Anything in the Old Town is of course very central, but the center of Tallinn is quite small, so you'd be able to walk anywhere comfortably (and I presume hotels not in the old town would be slightly cheaper). Viru Hotel is very popular with Finns (or at least used to be); it's right on the edge of the Old Town, and their prices are quite good from what I hear.
If you want bootleg stuff, there's a market place within 10mins walk from the center that the locals seem to frequent.
For Riga we used
http://www.balticsww.com/tourist/latvia/hotels.htm. Here's a good map of the city center:
http://www.virtual.lv/maps/baltic500000/riga_centrs.htm. For reference, the hotel we stayed at (Viktorija--on A. Caka Iela, off 13. Janvara Iela) was a 15-min walk from the Old Town.
There are lots of interesting museums in Riga (like I said, it was -25C when we were there, so we went to a lot more museums than we would've thought to go to), but the Occupational Museum is a must-see. The Old Town isn't too big, and the Tourist Information office has maps and brochures on what to see. What else... food was cheap; clothes and stuff were pretty much the same as in Finland (so a bit cheaper than in England).
There are lots of Finnish chains in both Tallinn and Riga (Stockmann's department stores, Seppälä clothing stores, Hesburger fastfood restaurants etc. one might want to steer away from for a proper Baltic experience. Likewise, restaurants at the mall in Tallinn (can't remember it's name but you'll know when you're there) such as Amarillo are also Finnish (well, so is the Sokos chain which owns Viru Hotel). Food's ok, but not really Estonian as such (the sort of fare you'd get at T.G.I. Friday's and the likes).
There's an excellent Indian restaurant in Riga. Of course if one lives in England that might not be too exciting, but here in the periphery of Europe one learns to seek out good Indian restaurants.
Can't think of anything else at the moment, but feel free to ask!
Oh, and learning a bit of local lingo is very much advisable--I talked to a friend who also went to Riga but didn't try to speak Latvian, and our experiences were
very different. I thought people were very welcoming and nice, and she said they were very cold and rude... I'd imagine the same goes for Tallinn.