192.com gives the above numbers at the above address. It also gives a nearby address:
Villiers House
Clarendon Avenue
Leamington Spa
CV32 5PR

with the following numbers:
Tel: 01926 331970 and 01926 450500
Fax: 01926 855553

01926 331970 is out of service and 01926 450500 has a message saying that it's DCS Automotive.

xCenta has the 450500 phone number and a fax of 450555. Perhaps they have numbers in between that.

I've Googled and found no common prefix we can try.

A Google of 01926 450 reveals quite a few numbers (belonging to other companies) scattered on the prefix. So it appears that they don't have many numbers on this prefix.

I've also found 01926 831401, which answers "You have reached DCS Automotive..."

01926 488201 answers "To leave a message, dial the mailbox number. To read your messages..." Dialling extension 213 gives us Philippa Weare's voicemail. Google shows that she is at DCS and gives a direct number of 488213 which is now out of service.

This gives us a way in to try DCS' extensions (which are 3-digits).