Hi Jools P,
I bought a package off of eBay and gave up with it in the end too. As Sixfingers says, the one I got was full of spelling mistakes and used Open Office. (Open Office a MS Office wannabe given away free by Sun Microsystems - it's not a bad package in itself and will save- almost - everything to MS Word format, but you are left with a few things that mean you have to go into the newly created Word document and reformat) Like I said I gave up with it in the end.
What I do now is use a pdf version I get free from ELECSA who also kindly add a cert number and my Part P ref, and using Adobe Acrobat (not Reader) I write in the details as needed. I can also blank out the ELCESA logo. To add my logo I have created my own letter head with logo, address etc and have printed up a stack of them on my colour laser printer. I then print the EIC on my letter head and hey presto the EIC looks nice and professionally produced. I also use the same method for MW certs.
It's still a bit of a fiddle and if I was doing lots of Certs every week I would invest in a proper package.
Cheers
Will