It is similar on Doblo 1.6MJs etc.
If you are lucky, a slim comination spanner tht size, or I sometimes use a Facom steel strap wrench that is quite effective.
Alternatively it may be possible to support the engine carefully using a rubber pad on a jack, then slacken the engine mounting so the the engine lowers down enough to allow your socket to get on through the wheel arch.
A small point when they are very tight the plastic nut tends to round off.
Motor factors can supply replacements , but there are several different types and filter designs I have found.
Finally when you succeed and are fitting the new filter and O ring to the cap, oil it well so the oil ring is less likely to stick next time and only do it up gently to recommended torque.