In the UK the main makes of Telescopes available these days are Celestron, Meade, Skywatcher and Orion, and there are at least 2 monthly astronomy magazines, Sky at Night and Astronomy Now where you will find more information and details of the main astronomical shops in the UK.
As to the competence and the level of expertise and support that you are likely to get from any one of these, that is a matter for you to decide. Look at the reviews, the on-line forums and talk to your local astronomical society if possible. Better still, if you are near enough to a shop pay them a visit and talk to them. The UK Astronomy Directory provides many links and news for UK astronomers whilst the Stargazers Lounge is the best place to chat to other astronomers and ask for advice.
Christmas - This is the time of year when small, cheap telescopes are on sale in large department stores, supermarkets and toy shops. The advice is that they are seldom suitable for astronomy either in terms of size or magnification, actual as opposed to claimed, and more importantly the Mount - see below. Thus you will see claims for a maximum magnification of 575 for a 76mm scope. Most of the proper astronomy stores now offer these cheaper scopes and will be able to give you proper advice and support that you won't get from the likes of Tesco - so stick to the specialist stores.
Mount: This is where the importance of the Telescope Mount is worth mentioning again. Without a stable mount, one which doesn't wobble at the slightest breeze or touch, which is what most of the cheap table top mounts do, you will never be able to see much, or do any serious photography. There are several kinds of mounts but two basic types.
Equatorial Mounts: These are tilted at an angle depending on your latitude and, for manual scopes are better for tracking, though they take a bit of getting used to. They range from CG1 to CG6 or EQ1 to EQ6, or similarly designations, which support increasingly heavy telescopes. Not surprisingly as the weight of the mounts increases so does the cost and a top of the range mount for a manual scope could be well over a £1,000, whilst for the robotic computerised ones, which may also include a pillar, we are talking of over £20,000!
Alt-AZ Mounts: These enable simple movements in both directions and are much cheaper than Equatorials, the most expensive computerised ones coming in nearer the £1,000 mark.
For Astrophotography the Equatorial Mounts are the preferred option because of the need for accurate tracking over long time periods - with accurate polar alignment only one axis has to be moved instead of the two which is the case with the Alt-AZ mounts.
You can, of course, buy from overseas, in particular from the USA where prices are usually much lower - typically the dollar price will be the same, numerically speaking, as the pound one. But import duties and taxes will have to be paid, and if there are any faults with the telescope then sorting that out may be expensive. This is also a factor to consider if you live a long way from a shop, though an increasing number of people buy on-line nowadays anyway.
Buying Second-Hand: Yes - there are bargains out there, in the magazines, local papers and on-line, from EBay or other on-line second-hand shops. But the advice here is much the same as with any equipment.
Always take advice if you can, particularly from knowledgeable members of your local society.