You need to take into account the following ,
Regulation 63 of “The Road Vehicles
(Construction and Use) Regulations
1986 (SI 1986/1078)” as amended.
Provides for the fitting of wings or
mudguards to vehicles to prevent mud or
water being thrown up by the wheels or
tracks.
63(1) This regulation applies to:
(a) invalid carriages;
(b) heavy motor cars, motor cars and
motor cycles, not being agricultural motor
vehicles or pedestrian controlled vehicles;
(c) agricultural motor vehicles driven at
more than 20 mph; and
(d) trailers, unless exempted by paragraph
(4).
63(2) Every vehicle to which this regulation
applies shall be equipped with wings or
other similar fittings to catch, so far as
practicable, mud or water thrown up by the
rotation of its wheels or tracks, unless
provided for in paragraphs (3) and (5).
63(3) The requirements specified in
paragraph (2) apply, in the case of a trailer
with more than two wheels, only in respect
of the rearmost two wheels.
63(4) Those requirements do not apply in
respect of:
(a) a works truck;
(b) a living van;
(c) a water cart;
(d) an agricultural trailer drawn by a motor
vehicle which is not driven at a speed in
excess of 20 mph;
(e) an agricultural trailed appliance;
(f) an agricultural trailed appliance
conveyor;
(g) a broken down vehicle;
(h) a heavy motor car, motor car or trailer
in an unfinished condition which is
proceeding to a workshop for completion;
(i) a trailer used for or in connection with
the carriage of round timber and the rear
wheels of any heavy motor car or motor
car drawing a semi-trailer so used; or
(j) a trailer drawn by a motor vehicle the
maximum speed
63(5) Instead of complying with paragraph
2) a vehicle may comply with Community
Directive 78/549.
So on a dry day its unlikely that you would be stopped and reported, but on a wet day , and depending on the view of the officer you could well be reported for the offence , especially in the way that you have modified the vehicle from standard and have not maintained the level of "mudguarding" as originally designed to comply with construction and use regs . JMHO HTSH