Unimog Club UK

you certainly can fuel the 900's up but id always take it to an official unimog dealer cause if you do it wrong it can be seriously expensive. we dont do it ourselves, we get it done by the pro's.
800's are getting harder to find these days as not many people wanted them because they only have 72 bhp rather than 88.

the reason it doesnt use a lot when its running the chipper is because there isnt a lot of load on the engine. Ive spoken to dad about this and he says its like driving up hill, the more load the more fuel used. hense with the chipper the fly wheel does all the work for the mog, so even though its revving its not having to work to hard.
when driving we get around 18-20 mpg. B)

congrats on the proposal  that 20 quid could go towards your mog! 
the mb tracs are awesome machines but a mog would be more practical for you, with a body and chipper etc...

As an admin i cant comment on any dealers, whether used or new.

Regarding the mog in holland, be careful, buying a mog thats cheap can often be an expensive choice, as it can cost a lot to repair them.
also find out what the specs are first, such as hours, disc/drum brakes, linkage, pto's, gearbox etc...
i might do a buying guide soon for the 900's.
also, front linkage looks good, but a din plate is much more practical. this is because with linkage the weight is moved foward a lot, where as with a din plate the implement is mounted right up to the front of the mog. like this



Note how close the Mulag mower is mounted to the Unimog, with linkage this would be much further forward. also with din plates you can get linkage kits that mount to them (although not so easy to find for 900's but could maybe make one :working:  ), giving you a wider range of implements to fit. plus with linkage the pto rotation is wrong for any implements that are usually on the back, so you would have to get a reverse drive box aswell.

But i would say to find out more info and if it sound likes its worth it and you can afford it then go take a look at it it'll be a holiday at least

cheers, Brian   

EDIT: click the pic to view video.