If you haven't made contact with them yet, then read the reviews.
http://www.ciao.co.uk/Reviews/Enact_Direct_Legal_Solutions__5673063

Enact belongs to First Title, who have offices in Leeds, Bromley, Euston, Camberley.
http://www.firsttitlegroup.co.uk/company/location.html?office=leeds
Contact Us
If you would like to know more about First Title Group and the products and services that we offer, please contact us as follows:
General Enquiries
Main Switchboard:   020 8315 1300

Remortgage Enquiries
Telephone:   020 8460 8001


The difference between the P.O. box and First Title is about 600 yds, so they probably use the same office, which is
Cardinal House, 9 Manor Road, Leeds LS11 9AH

There is a company called Enact Properties Ltd, also in Leeds, involved in the same line of business.
SOVEREIGN HOUSE SOVEREIGN STREET
LEEDS
WEST YORKSHIRE
LS1 4BJ
Business Directory
0113 209 2000
0113 283 2060 fax

A further look http://www.secinfo.com/d14D5a.v1nHx.b.htm shows them to belong to First American, along with
enact Conveyancing Limited
enact Holdings Limited
enact Properties Limited
enact Trustees Limited

Enact have a block of 0870 numbers which map to a block of 0113 numbers. The last four digits of the 0870 number is the internal extension number. Use the following to work out the 0113 number for any Enact 0870:

0870 835 2xxx = 0113 384 2xxx
0870 835 30xx = 0113 384 14xx
0870 835 31xx = 0113 384 15xx
0870 835 32xx = 0113 384 16xx
0870 835 33xx = 0113 384 17xx
0870 835 34xx = 0113 384 18xx
0870 835 35xx = 0113 384 19xx

As mentioned above, the only exception to this is the switchboard, 0870 835 2000 which routes to 0113 384 2001.