The number in the database (01344 860 456) for that address appears to be a head office/reception number.

Assuming sales is dealt with at the same address then if you have inclusive mins on your landline try numbers around 01344 860 456 as chances are they'll use numbers around that range.

A 192.com search comes up with only a few geographicals as follows:-

01344 860 456 (mentioned above)
01344 372 767 (fax)
01344 378 000

A search of their website

here

revealed that they use numbers for Direct Dial as 01344 37 xxxx.  Therefore, I would have thought 'Sales' is on a number range around 01344 37 xxxx or nearby 01344 860 456.

Update:

A little thing you could try and that is ring someone on 01344 37 xxxx and if they don't reply sales then ask them for the extension number of sales.  If someone does provide it to you without thinking then simply dial 01344 37 + ext number.

I tried something similar searching for Bosch's geo and having tried a few times (most just transferred me to switch), one person actually gave me the extension without thinking.

378002 - meeting room
378005 - voicemail

373000 - reception as quoted by person answering 8002
860456 - number for Reception, "ask to be put through"

0870 907 3354 is the Dell Public Sector sales line but 353 12043354 is some other company in Ireland's direct internal extension.