If you don't personally value or want the options, don't bother getting them.
Simple fact is you won't get the money back that you pay out for options.
They will make it alot easier to sell though. I recently sold my cooper and found most people didn't know the specs inside out. However, lots of people asked about and wanted Air con. So maybe this is worth paying for.
About voiding the warranty that's BS
Why not get the standard headunit and fit a Sony T69 6 Cd changer in the boot? With a connects2 adapter this works with your mini headunit and costs from around £160 on the internet and approx £230 in halfords.