1. Driving - The whole island has a fantastic road network that is virtually entirely free (a couple of tolls bridges/roads here and there). Whilst congested around major public holidays and at rush hours around inner cities like anywhere, you can get from A to B by car very easily. The development of the roads in the 1950'60's came to the detriment of other transport networks, notably the Railways which are now plagued by reliability issues. This makes car hire a must, giving you both the freedom to explore and make the most from your trip.
2. Buy An Umbrella - Without wanting to put a dampener on things, outside of the "summer" months in July/August there will be days when it rains. Be like the locals and stick a cheap compact umbrella in your bag, or if hiring a car you can truly be a native with a large stowed golf umbrella! So choose best months of come.
3. Black Cabs - These are notorious for charging passengers more. So if you're looking to save some cash or not waste your cash then calling a private taxi firm will do the trick. Black cabs are prevalent in most parts of the country, but you will pay a premium. Journeys of anything over a few miles will become very expensive in any respect, and you should consider alternative means of transport. If negotiating distances such as those London and Edinburgh, opt for air travel - or car hire is again a more economical option.
4. Rarely Tip - It's not that we natives are cheap (arguable), it's just not embedded into the mainstream culture. Outside of decent restaurants and perhaps a handful of other places, tipping is not the norm. If you feel you get great service then by all means tip, but the recipient will often be quite surprised. The isles are pretty much in reverse to North America and continental Europe in this respect, where tipping is very much the norm. On the other side of the coin, this is perhaps 10% you don't need to factor into your travel budget!
6. Drinking - Friday/Saturday nights are big social affairs, and whilst this can bring its own problems the UK has some of the best restaurants, pubs and clubs in the world. Guys be prepared to embrace pints (567ml) of beer, cider, bitter etc, ladies beware that glasses of wine come large as standard. In mainstream chain pubs you can get all popular international and domestic brands. In traditional, freehold or country pubs you will find more regional brews that should be sampled over any mass produced offerings. The Good Pub Guide is a leading authority on such matters. Clubs are generally the place to drink spirits and cocktails of varying quality, wholly dependant upon the venue.
7. Eating - Despite the faux rumours about British food, it is much improved, particularly in England. Most cities can now boast many top restaurants. That said, the UK lags noticeably behind other European nations in terms of quality and value of food. Traditional roasts (eaten on a Sunday), as well as regional dishes depending upon where you are staying are always a safe bet. Aside from this there is no shortage of multi-national fast food for the budget crowd, and the ever popular fish and chips are available virtually everywhere with regional variations.
8. Travel by Air - The worlds largest airline Ryanair are based in Ireland and operate from most UK airports. This is the cheapest and most efficient way to see other parts of Europe and major UK cities. The UK's regional airports are numerous, easy to access (Heathrow aside) and often overlooked. Booking in advance is often the key as prices escalate nearer the date and as seats become fewer.
9. Dialects - Think you won't need a phrasebook? Think again. The UK is home to not only more than one language, but also many locally entrenched local dialects. The Birmingham, Newcastle, Welsh and Yorkshire accents should prove interesting, if occasionally a challenge for any newcomer.
10. Shop Around - The inhabitants refer to the high price of most products as "Rip off Britain". Don't be tempted by needless spending and waste your cash, which can be easily done in London around tourist areas. In fact London is an inflation bubble in its own right, and should you make it outside, your wallet will thank you. Shopping around for food is easily done and often ultra competitive anyway, but make sure you have researched your hotel online so you're getting the best deal - as almost all hotels charge more at the counter for "walk ins".
I hope this helps you during your stay!