Think i'm over thinking this situation. 
I don't think so, but don't forget to save a sample to send off for analysis. 
The only options i have that i can see without causing too much hassle..
1. Take a gamble with the bog method. (Too risky in my eyes)
2. Put the waste in bottles or a container (with flushing there will be a lot of liquid) to take to the waste centre some 30miles. But I don't know if the take antifreeze haven't checked. This is only a possible option.
3. Leave it as it is and to hell with all this just add a but of new red stuff (I like this option

)
4. Take it to a garage to get done.
5. Sell it on eBay for 0.01p & free delivery or collection only, someone's bound to buy it, Those eBay sheep will flock.
6. ...........................................................................?
7. ...........................................................................?
....I'll take a sample with a syringe also for good measure
