Can't recall who we got the one for our last house from, but it was made by Brabantia, and cost well under £100. Despite having a big sign on it saying "post box", some dozy delivery folk stood in front of the adjacent letter box-less front door, looking puzzled, and a couple just left stuff on the doorstep. Twats... Letter plates in front doors allow draughts to get in, heat to get out, and give an opportunity for scumbags to put undesirable objects or substances into your house.
Considering getting a parcel sized one for our current abode, to save the folk having to open the gate and walk 10m to the front door, and close gate, etc. As the postie has to use a van round here (very, very rural) its all a bit of a palaver.