Why has my Citroen Berlingo suspension gone 'low' ?

2003 2.0 Diesel Turbo Belrlingo with ABS 110,000 mile

Original back axel had to be replaced as banging / knocking noise was getting worse. Quoted almost £500 + fitting + vat from Citroen dealer, so purchased second hand axle from breakers yard £138 and fitted by local man for £250, so much more affordable. Breakers Yard assured me axle was from a Belingo for that year and gave 3 month g'tee. All seems ok and car runs OK BUT it seems very low on the suspension, it sits well down and does not seem to have the clearance at the top of the wheel , but as I say, seems to run OK and no more knocks and bumps from the back. Any idea why it should sit low ? Any ideas /thoughts would be appreciated.
Thank you for your time.