As promised previously, I've posted on saving money in London
General travel tips.
1. Take less stuff. All these places are major cities. Anything that you need that you didn't bring you can aquire.
2. Don't tip in pubs in London and Dublin. Its not done. When I went to the States on a BUNAC exchange program, they had to explain to us the immense importance of tipping in the US. By all means tip waitresses and bell boys(?) and maybe cabbies.
3. On the subject of pubs, if you want a drink at a pub in either Dublin or London (or anywhere in the British Isles) you should probably go to the bar. This would never have occurred to me, but apparently people from elsewhere have been known to sit at a table for ages in a pub wondering why no one came to serve them. Table service does happen but its not common.
4. Expect things to be different to what you imagine and be polite about it. Although I'm sure you would be anyway.