There is a Mondeo cargo net that can be easily installed / taken out.
No drilling holes and rattling like with the metal cargo barrier.
I had one on my Mondeo Mk3 wagon, and I have one on Mk 4.5 ZETEC wagon as well.
Mk3 version is on the picture below, Mk4 looks slightly different, but both will fit Mk4 Mondeo, so either one you can get your hands on will work.
Ford P/N: AM7S7J N613F33 BA
Ford is asking 400+ for it, on eBay you can get one for around 140 pounds UK. I picked one up, brand new, on eBay AU for 65AUD + 20$ for shipping.