The key thing to remember when buying a tow bar for your car is it needs to be ‘type approved’. This means it must meet the relevant regulations and be designed for your car. Type-approved tow bars have a label with an approval number and details of the vehicles it’s approved for.

Without seeing the two bar from the independent garage I cannot say if it's designed for your car or not. But it's important to check this before proceeding as a non-approved tow bar may damage the vehicle. Likewise, the BMW dealer may install additional gearbox fluid cooling that will benefit your car when towing heavy loads, while the independent garage may not.