You fancy a change but still like the XF - you're wondering about wheels and thinking of an SRT6 front lip...
Here's a thought - you can achieve all that by 'upgrading' to an SRT6!
Same car, yet different - different wheels - and the lip is included!
Plus the significant performance gain - and insurance is virtually the same - in my experience.
Obviously much rarer but they do come up - and most UK SRTs I've seen for sale are usually well cared-for enthusiast cars with comparatively low mileage - which should satisfy your OCD side!

Regarding the fuel smell - I read somewhere on here a while ago that the primary fuel line (from the pump) can split with age - might be worth checking...?