So it looks like the £250 i paid (was actually like 310 euros roughly) was an extra charge on top of the 109 i paid to upgrade.
So i have actually paid over 550 euros to rent that for 10 days, i now feel slightly sick..
550eur is still very good value for that car in Europe. I am still somewhat confused as to why they gave you (or why they had) a Belgium plated car though....