Two questions MUST be answered so that we can answer your question.
1) What type of operation are you running, Part 91 or 135? If you're 135 you've got some other issues...
2) What is your budget. You can go cheap with a COTS (commecial off the shelf) Tablet PC, or go with something that is purpose-built and a dedicated EFB, depending on question #1 and
where you'll put the EFB.
In the meantime, here is some required reading if you haven't already:
FAA AC 120-76A.
Oops...just noticed you're UK-based. Disregard the above if that's the case...