Having a similar problem to my 1.4 LT wagon in Australia. Thanks to being spun on the motorway (another story) I had the front bumper replaced and rear repaired. The blind spot monitoring and self-parking hasn't worked since. It picks up everything the manual says it shouldn't (trees, on-coming traffic, barriers) and doesn't park properly (it tries but runs into the kerb).
The dealer is a bit stumped but current theory is replacing a couple of the sensors. Failing that it'll be hands in the air I think.
Anyone got anything else to try? I put the car in neutral and walked around it and it seems that all sensors actually work, but it's not processing the information properly and filtering out.