For any device from a well-known brand, plugging a device that wants 1A into a 4A charger will not cause any problems. The device decides how much current it will take, and the charger can't force through more. The other way round may cause the charger to overheat.
I'd be very wary of buying a random cheap charger. While I'm happy to use cheap generic stuff in lots of situations, there are a lot of rubbish chargers out there. http://www.bbc.co.uk/news/uk-27390466
gives some examples. Modern electronic chargers rely on electronics and good design to keep 240V separate from 5V. Cheap products use cheap components and have poor design. A fire or 240V getting into your devices are very real possibilities.
I'd also keep an eye on your Poundshop 4-way cable. If you end up plugging in 4 x 1A devices, that's 4A going through the plug, which is a lot for USB, and I'd be surprised if the plug was of good enough quality. I have had several USB extension cables from Poundshop (it makes it much easier to use a phone, etc, while it's charging). Only one now works, the others have all failed, and something as simple as an extension lead shouldn't really fail.
I'd suggest what you need is a branded charger of a power equal to the sum current of the devices you want to charge simultaneously (which may be non-trivial to find out). If this looks expensive - which it may do if you limit yourself to non-dodgy sources - consider charging sequentially. Be aware that Apple have their own alternative to the USB charging rules, so your iPod may charge slowly on an non-Apple charger.
Final thought. If you're buying a charger specifically for use in Europe, I'd buy one with a continental-style 2-pin plug, and avoid the clunkiness of the UK 13A socket and an adapter. I bought one in a French supermarket (after leaving my adapter behind at a campsite) and it makes for a very neat solution.