Section 59:
Vehicles used in manner causing alarm, distress or annoyance
(1) Where a constable in uniform has reasonable grounds for believing that a motor vehicle is being used on any occasion in a manner which�
(a) contravenes section 3 or 34 of the Road Traffic Act 1988 (c. 52) (careless and inconsiderate driving and prohibition of off-road driving), and
(b) is causing, or is likely to cause, alarm, distress or annoyance to members of the public,
he shall have the powers set out in subsection (3).
(2) A constable in uniform shall also have the powers set out in subsection (3) where he has reasonable grounds for believing that a motor vehicle has been used on any occasion in a manner falling within subsection (1).
(3) Those powers are�
(a) power, if the motor vehicle is moving, to order the person driving it to stop the vehicle;
(b) power to seize and remove the motor vehicle;
(c) power, for the purposes of exercising a power falling within paragraph (a) or (b), to enter any premises on which he has reasonable grounds for believing the motor vehicle to be;
(d) power to use reasonable force, if necessary, in the exercise of any power conferred by any of paragraphs to (a) to (c).
I see no mention of a PCSO having these powers, nor can I find any amending legislation.
Although a private firm may effect the removal, they are not "seizing".
I'm not saying I'm right in this, but the question raises interesting points. Buenchicho may have a view.