Inspired by Dave's Shindig video I'm thinking of taking a few photos and film with my phone on BB200

To make sure I don't run the phone down completely I'm thinking of getting a spare battery, looking on the tinterweb they seem to range from £4-£30! Will a really cheap one die straight away, any decent website recommendations?

Oh yes, phone is HTC One SV

Cheers

Get an OEM one supplied by Amazon.

Having said that, why not just get an Anker or similar power bank?

I'd second an anker 3000mah external battery. Will give you a whole extra charge and a bit extra. Plus will charge anything else you have that runs of a USB.

I have two in our household. Both work flawlessly.

I got a "high capacity" battery for my HTC Wildfire, I think it was something like 2400mAh instead of the standard 1800mAh, and it used to go flat at about the same time every day as the old one did.
I then bought a physically bigger 3500mAh battery that comes with a deeper back cover and it really has made a big difference. I haven't done any proper fully charged to flat tests, but if I forget to charge it overnight, it will last at least two days, when the original battery would die after about 16 hours.
http://www.ebay.co.uk/itm/3500mAh-Exten ... 1429337598

It's worth paying more for a decent one. The cheapy ones from eBay that have "eleventy million" mAh tend to die fairly quickly.

I bought a genuine Samsung replacement one for my S3 for about £20 and a double capacity one that needed a new back for the phone. The double capacity is from "Mugen power" and it will let my phone Strava for 2 days bikepacking so I can save the route. That's with everything on in the middle of nowhere so if I put it into Airplane mode I'm sure it'd last longer.

Probably going to go for one of the power bank type things next though. I'm about to replace my phone and the batteries will then be next to useless. May keep it as a navigation aid though as it's got Memory Map on it.

I have a 10000mAh one that does me for a week of iPhone and GPS, but it's quite bulky, so I bought a cheapie on eBay for £4 which will give me three Garmins or a Garmin and an iPhone charge - perfect for an overnight