i have the same box,and have had to use a different trolley,the one i am now using has two adjustable front legs that extend outwards to accomodate the footplate assembly,the wheel shafts also adjust outwards, i have to remove the two back legs on the box,plus the retaining screws to get it to sit flat on the trolley,
i do not know the makers name,but it is a fairly common design,and it only cost about 30 quid,compared to 80+ quid for the milo.
hope this helps
Give the guys a call at Kc Angling a call mate they make a copy of the Milo trolley wich I and a few big named anglers consider a better trolley than the genuine Milo.
They are better built and stronger too.
I haven't been in there for a little while so cant tel you current prices but it cant hurt to give them a bell.
its stupidly fiddly, a standard footpump (probabaly the most universal type) wont fit onto the valve and it doesnt stand up by itself!
when i mean fiddly... you have to lower the rear box legs, clip the bottom half of the trolley in (easier said than done!) then support the trolley in the correct position while you lower the arm that comes down onto the box, then reduce the size of the rear legs... and if that isnt done correctly the box is attatched to the trolley until you hit it!