Argos - -probably alright, fairly good value for money, but as with the Lidl, look closely before you buy at the ease of the hitch, folding.
Koolstop - very bright colours, said to be too likely to tip, but we didn't have that problem with ours. See below for more about our actual experiences with this one.
Little Man - A German make. Friend bought one of these on Ebay, for £60 plus postage (about £15 from Germany). It attach to the chainstay bike, has a solid (metal base), LOTS of luggage space and folds down quite creatively (sort of a butterfly fold). A bit wider than some of the others on offer, and probably heavier with that metal base. But friend has been happy with it, seems a good choice for those on a budget.
Philips/Stevens - these often go for a pittance on Ebay.
St. John Street Cycles/Thorn: apparently do a trailer rather like the Burley but a lot cheaper.
Wike: Cheapest of the top quality options, also best (most visible) colours. Has the simplest & cheapest stroller conversion kit if you only need this option occasionally. Sells direct from (Canadian) manufacturer/own website to cut costs and increase quality of customer service. Got rated highly in product review by Adventure Cyclist.
Burley: an Oregon make, the champ, the favourite, the original. Wike see this as their main rival. Provides a limited life-long guarantee, so only to the first owner, and that doesn't cover fabric, either (apparently) according to one of the reviews on Epinions. Beware therefore if you buy one 2nd hand that the guarantee doesn't come with it.
Chariot A Canadian make, rebranded as Rhode Gear and (I think) Trek in the USA. Nearly as popular as Burley. Slick website. Same warranty conditions as Burley. One thing that confuses when you're shopping for a Chariot is that they are usually advertised & sold as 'Chassis only'. That's because to make it into a cycle trailer you need to also buy the cycling conversion kit, otherwise you could be buying it to use for hiking or skiing or jogging, whatever! At any rate, always assume that the basic price is for the box plus wheels only, to actually use it for any activity, you have to buy something else, too. Adding up the bits can make the Chariot more expensive than the Burley, but I notice that REI have scaled their prices so that the Burley (which comes as a cycle trailer) and the Chariot + cycling conversion kit are the same basic price. Maybe that's deliberate strategy on Chariot's part.
Winther: this is a Danish make, priced near 700-800 euros (so around £450) when we were looking. Has a solid floor. Reading their website is a good chance to realise how close Danish is to English & Scottish! I think this is probably an excellent product, may even be much superior to the others, but admittedly found it hard to research because I don't know Danish.