someone has kindly put a 2inch scratch on my rear bumper which has gone too deep to polish out, is it worth just buying a touch up pen or have the bumper resprayed which I'm a bit worried about incase the black doesn't match completely

If you are the practical type try one of the Chipex repair kits maybe? http://www.chipex.co.uk/

Think these are a step up from the old 'bottle and brush' touch ups. 2008 MY Java Black TDV8 HSE

Having tried meticuously to touch up my Sumatra Black RRS, I think if you want it gone, a respray is the only way, you just can't recreate the metallic flake distribution with a repair unless you are a dab hand with a mini spray gun  ON THE WAY: BMW F21 M140i
MERCEDES GL350 - Metallic Navy Blue w/Grey interior

GOING: BMW F31 335D MSport+ xDrive Touring
GONE: Land Rover Discovery 4 HSE - Stornaway Grey w/Black Interior (wish we'd kept it )
GONE: BMW F10 520D MSport - Carbon Black
GONE:MY12 RRS SDV6 HSE Sumatra/Ivory/Grand Black Privacy glass

Yeah i agree but im worried about the colour not matching with the respray, think the chipex could be worth a go first nothing to lose really. I wonder if anybody on here has actually tried chipex?

Agree, you're got nothing to lose if your back stop is a respray, I've had good results building the paint up with a cocktail stick as the applicator. Took a couple of weeks, then I gently sanded it back (2000 grit) and then polished it back up.

Problem on my RRS was that it was on the wheel arch and very difficult to sand, if it's a flat surface, with a unigrit sanding block and a bit of patience, you might be able to do a good enough job  ON THE WAY: BMW F21 M140i
MERCEDES GL350 - Metallic Navy Blue w/Grey interior

GOING: BMW F31 335D MSport+ xDrive Touring
GONE: Land Rover Discovery 4 HSE - Stornaway Grey w/Black Interior (wish we'd kept it )
GONE: BMW F10 520D MSport - Carbon Black
GONE:MY12 RRS SDV6 HSE Sumatra/Ivory/Grand Black Privacy glass

You might be able to get it smart repaired.

I had 2 front smart repairs carried out on my previous RRS on the front & rear bumpers and after I couldn't tell where the repair had been carried out. Saved a fair bit compared to having both bumpers resprayed.

Although I had this carried out by a local reputable bodyshop and left the car with them at their premises as opposed to one of these mobile smart repairers eg. chips away etc. 2014 L405 SDV8 RR Autobiography

2012 RRS SDV6 HSE -Orkney Grey with A/B bodykit - Now Gone
2007 RRS TDV6 HSE - Zermatt Silver - Gone