Firstly, you'll love it. The UK is a great place.
You don't mention the kinds of venues you'll be playing - there isn't a huge market for live country music in the UK, so I'd expect it to be smaller, specialist venues, social clubs and so on. The crowds will be enthusiastic and probably quite drunk.

Make sure to talk to people, enjoy a pint or six yourself and be ready to talk a lot about where you're from. Most people will think you're American, so you'll have to set them right - most Brits don't know to listen for the telltale Canadian raising!
In terms of technical issues, the UK's national grid is 240V/50Hz, so make sure any electrical gear you take with you (amps, effects, etc) either has a switching power supply or that you have a good step-up transformer available. If you're taking a laptop or mobile phone charger with you, their chargers/power supplies should work straight off with just a plug adapter (you can pick these up at the airport). Also, regarding mobile phones, don't run up massive bills by using your Canadian phone - go to any mobile phone shop and pick up a cheap pay-as-you-go phone. Shouldn't cost you any more than £20 for a basic one. I'd suggest the whole band get one each for staying in touch. There's quite a few mobile networks, but O2 and Orange are probably the best. Wi-Fi is fairly abundant, most hotels, pubs and coffee shops will have it for free. Or you could pick up a mobile hotspot for £60 or so from a mobile phone shop that will give you mobile Wi-Fi with 3G speed.
For getting around, I'd imagine you'll have a bus laid on, but there's good public transport in most bigger towns. Do go out and look around, and don't be afraid to ask people for directions and stuff (as long as you're outside London - they can be a bit brusque there

). If you're in London, make sure to see the sights - get a One Day Travelcard to get around, as this one ticket will get you unlimited use of the trains, the buses and the Tube all day for about £8. The London Underground (Tube) goes almost anywhere you'd want to go in London and is really easy to navigate. If you're in London, pay a visit to The Gallery in Camden Town to play the best selection of basses in London - it's a 5-minute walk from Camden Town tube (
www.thebassgallery.com). Remember to look right, then left when crossing roads (cars drive on the left in the UK). It'll probably rain a fair bit, so make sure you've got an appropriate jacket. Britain is stuck halfway between old imperial measures and metric - distances on the roads are in miles and someone will tell you their weight in stones and pounds and height in feet and inches, but you'll buy fuel by the litre, food by the kilo and the temperature on the weather forecast will be in Celsius.
Ignore the misinformation about British food - there's some great food out there. Lots of awesome Indian, Greek, Turkish and Thai food too. Indulge in pub lunches (Wetherspoon's pubs have a great food menu). Go to a greasy-spoon cafe and have a full English breakfast with a big mug of tea. Get friendly with the service station shop (McCoy's crisps, Ginsters pasties and Mars bars are a British touring musician's best friends). If possible, go to the service stations with M&S Food, as they have the best sandwiches ever, and avoid the ones with Little Chef restaurants. Make sure you take the whole band out to an Indian restaurant for a post-gig curry with all the trimmings. If you're dying for a taste of home, most of the fast food chains you know are there, albeit with slightly different menus. But a Big Mac is a Big Mac anywhere in the world.
Things to be wary of - drunk people, basically. Most Brits are fine with a few drinks in them, but you will find some just can't handle their drink and get violent. We call them "chavs". Fights outside pubs aren't an uncommon sight late at night. Just steer clear and make sure you're in a group if you're out late at night. There's very little gun crime in the UK (handguns are illegal) but there are lots of idiots with knives, so be careful.
You'll be over in the height of the sports season - there'll be lots of big football games on and the Six Nations rugby tournament will be in full flow. Make sure you go to a pub where they're showing the games, have a few drinks and enjoy the atmosphere. Pay particular attention to the rugby - this is what American football would be like if the players didn't wear pads and didn't stop every 20 seconds.
Us Brits love to make fun of people in a light-hearted way, so don't take it personally if you get the occasional comment. You'll probably be alright though, since, in my experience, Canadians are fairly au fait with the concept of "taking the piss". We'll make fun of ourselves as much as we make fun of anyone else. We're very sarcastic and we swear a lot, but we love to have a good time.
Hope that helps...