6 months is an awfully long time, however as it was such a minor knock, the third party just probably hasn't got round to booking their car in for repair yet.
To put it into context, I had a fairly bad accident in February, I caused £9.5k worth of dmg to my car, wrote off 2 other cars & caused 2 (minor) injury claims. I was going on holiday the following week, when I got back from holiday my car had been repaired & since collecting it, I have heard nothing more from my insurer, nor do I expect to. Although by now, they will have paid out for the 2 cars I wrote off, & also the injury claims - this is what insurance is for, insurers do it all for you!
If I were you, I would ring your insurers & ask them to get in contact with the third party insurers to ask them whether their insured still intends on claiming (for all you know, they may have sold the vehicle or anything in that time period). If they are still claiming, ask them whether they have had an estimate yet - they should have either a) had one of their nominated approved repairers assess the car or b) received an estimate from their insured for the repair. At least you will then know the costs involved, although i do fear they may well replace the bumper, as is so often the case with these sorts of claims. You are probably looking at a few hundred pounds at least.
You might also find that the repair has been carried out & the claim done & dusted. Just give them a ring, they will be able to give you all the info you need.
