Our drop shipping Bonus PDF guide has a lot of information about what to do and what not to do when drop shipping generally.
As far as using an international drop shipper to send products to your customers in the UK goes, first you'll need to find a drop shipper willing to send products internationally. International shipping will also bump up the cost to your customer, so I would make sure you have explored all local avenues first.
Secondly, seeing you know pretty much exactly what products you'll be drop shipping, give Customs a call and ask them about the duties for importing single quantities of this product. Your customers may have to pay duties when they receive these items, so it's important you know what these duties are (at least approximately) and any other taxes that may be charged, so you can clearly state these in the listing description.
Hope that helps :)