Just to be clear, you have three choices of satellite box, in part depending on whether you only want to watch the UK channels and how far you are travelling.
The 'cluster' of satellites at 28.2E broadcast direct to the UK. Your Sky box, a Freesat box or a generic satellite box will all receive the SD free to air channels. The HD channels and some others need a HD box. The difference in practice is the Electronic Program guide. Your Sky box will give you the Sky one which includes all their subscription channels so you may have to plough through it. The Freesat EPG only carries about 200 radio and TV channels and, apart from the first few, the channels are numbered in a different sequence. Generic boxes do not have an EPG but only display the Now and Next information for each channel. All the channels have four digit numbers and you will have a whole series of duplicates for the various BBC and ITV regions.
As you will, presumably, only be wanting to watch UK programmes, your Sky box will be perfectly adequate. You just need to attach a set up satellite dish. The dish has two main parts, the dish itself and the 'LNB', The latter is the receiving assembly that attaches to the dish's 'horn' A cable goes from the LNB to your set top box. If you have a basic box, you need a 'single LNB'; if it is a recorder, you have to have a 'dual LNB' and a double lead for it to fully work. The dish, LNB, cables and the fixing hardware are sold separately for home use. As you will see from the links, some places sell specialist dishes with stands or tripods for touring use as complete kits but at greater cost than buying separate components and more DIY fittings like the poles and clamps described in another link.
If your Sky box gives you all the channels you want, use it rather than buying a Freesat box as aligning the dish needs to be slightly more accurate for Freesat (technical reasons) Other satellite clusters are available over the continent so you could, for example, keep up with the news on Sky or the BBC World Service TV by accessing one of them. To do that, you would have to have a Freesat box in a special mode or a generic box..
