The standard battery that comes with any camcorder (other, possibly, than mega-expensive professional models) is unlikely to give you anywhere near to 3 hours recording time. So it would make sense to allocate part of your budget to one or more (preferably high-capacity) spare batteries.
The Panasonic HC-V770 gets good reviews for a budget camcorder. It's available from Amazon for £335. The 20x zoom lens has the 'wide angle' end of its range at 30mm (using the '35mm film equivalent' way of measuring it), which is about as wide as you can get without encountering the 'fish-eye' effect of a super-wide angle lenses. It's got a socket for an external stereo microphone. You only get about an hour's recording time from a standard battery (VW-VBT190, about £26 for a Duracell one) but you can get double that time from the long-life version(VW-VBT380, about £30 for a Duracell one), so you could buy the camcorder and some long-life batteries, still staying within your budget and with enough left over to buy an external mike.