I have an Abbey 540 Freestyle 2005 which should have the same mixer tap.
First of all if the swivelling spout has gone so tight as to move the base on the work top you need to cure the root cause of the issue.
First of all, take the sink out. There's 3 torx type screws securing the bowl to the work top. T15 bit I think. Then there's just 1 slot screw holding the waste trap to the sink.
Now depending on your specific van you will need to take out the draw in the cuboard between cooker and fridge, or take the fridge vent cover off outside. it's the top one you want off and in the top slot there are 2 tabs which need pushing towards the center. Take the mesh fly guard out too.
Now depending on the fitting, you should be able to see and un do the securing nut from the tap base.
To strip the tap down. On the hand lever there are 2 hot/cold markers which just prise out with a stanley knife blade. Inside there you'll find two 3mm af hex allen grubscrews that hold the handle to the tap valve. They are a right fiddle so take your time there. Now the handle does lift off but might be a tight fit. After that it is quite easy to take the rest apart as there is obvious fixings. that hold the hinge and valves together.
On re-assembly after cleaning, apply some vasaline to the swivel parts to prevent further trouble.
Good luck.