What on earth for?
I suggest that you have another talk with Evesham. Tell them that the machine isn't 'as described' in your opinion, and that you want it exchanged for another computer. Be polite but firm, and don't threaten them with Watchdog (who would be very unlikely to show much interest anyway). This can be a simple matter if you handle it that way. The courier's failure to show up to collect the machine isn't acceptable, and you must tell Evesham that. The company generally has an excellent reputation for customer service, and I hope that you'll soon be feeling much happier.
If you aren't you know where to come, but please keep the dialogue going with Evesham.