We're just finishing doing the bathroom on a very tight budget, and am about to move onto the kitchen.
My best tip would be to shop around, most especially at independent shops. We looked at BnQ, Homebase, Bathstore, Topps Tiles and IKEA, and ended up using local independent trade-style shops for the suite, taps etc and tiles too because we found stuff much cheaper, and better quality at the trade shops.
For tiles, we found Topps tiles to be very overpriced, and wasn't much impressed by their range either.
We discovered a brilliant place called Al Murad. Their prices are much better than any of the big chains (for the kinds of tiles we were looking for anyway) and their range is much nicer.
Don't let their appalling website put you off! Definitely worth a visit if there's one anywhere near you.
www.al-murad.co.uk/branch.html
Where are you? If you're in London, have a look at Chris Stevens towards the Archway end of Holloway road (N7), and ask if you don't see what you want there. They have loads of catalogues of baths etc which they offer really decent discounts on. We got a perfectly decent toilet from there for £45 for example. (And she came in a box labelled "Becky" which makes me smile - and she'll be called Becky" forever now I suspect )
I just ordered the towel rail today, so I can't say if it's any good yet , but it was cheap! www.firstbathrooms.co.uk/