Lock bumping is putting the safety of your home at risk. Bump proof cylinders are widely available; they may seem expensive compared to a standard lock but a small cost in comparison to the consequences of a burglary.
Having top and bottom mounted locks will provide greater protection against the doors being sprung.
Most PVC-U replacement front doors come fitted with very cheap locks that can be bumped open, so it might make sense to upgrade to a higher-quality cylinder lock incorporating some kind of anti-bumping system.