My OH bought a dual sim card Blackberry clone about 2 years ago via ebay.
It would appear quite a useful feature if you like swapping between networks – which avoids fiddling about with sim cards. You can even get tri-sim card phones now.
I can’t recommend any particular model – you need to decide which features you require and how much you are willing to pay. On a general note, I would say that the quality of such electronic devices from china is very good, and prices can’t be beat. If having your phone operational at all times is important, check that it is supplied with a spare battery.
A few things you need to be aware of:-
You could be stung for import duty/tax and an inspection fee which could easy add £25+ to your purchase price; although I have never incurred this due to the sellers declaring a false value for the goods and/or customs not looking to closely.
Many of the phones are sold with a poor quality mains charger; if you do use the charger supplied, my advice is not to leave it unattended and better still, buy a replacement from a reputable UK source.