And BTW I too can get rid of engine oil at the local waste collecting centre (we call them “containerpark” in Dutch) at no cost.
Same here, and special days for neighborhood collection. Most people take their used oil and batteries to auto parts shops anyway because they are open longer hours, seven days a week, and are closer. This hasn’t stopped me from accumulating my own little oil reserve, and also a store of ex-batteries from the time before I discovered the value of a battery tender on nearly everything… 
Must do something soon 
It depends on the maintenance program, aircraft type & weight, kind of operation etc. It would be a good idea to discuss this on forhand with the CAMO or maintenance company.
First to keep the aircraft in the controlled environment the CAMO will have to issue the work order, they can delegate a 50 hour check to any EASA part M Subpart F company or for UK registered aircraft to the pilot owner.
What the pilot can’t do is certify any items outside the LAMP maintenance program so items that are AD’s have to be released by some one with a maintenance licence.
As most AD’s are on a 100 hour cycle and we are talking about 50 hour checks the answer about pilots certifying 50 hour checks depends on were the aircraft is in the maintenance cycle.
First to keep the aircraft in the controlled environment the CAMO will have to issue the work order
What would be the typical charge for doing that?
It depends on the contract you have with the CAMO. Could be a single fee, or could be included as part of the annual fee
I would consider the work order issue to be covered by the annual fee.
I may be being obtuse here, but surely if you are off on a long trip you check if you have the hours available to do the trip before you leave, and if you don’t you either get an extension or do the maintenance work before you go.
We keep a simple tech log sheet with an “hours to go till next check” column in it, which is revised after every flight.
On our bigger aeroplanes where maintenance is complicated there is tracking software which predicts maintenance activities, AD/SB compliance etc.
