Adding things or updating. and seat covers

Hi just got a 2007 1.9tdi estate. Is there any cabling which can be used to add things ie a power socket in the boot area? Electric mirrors etc? Guessing rear electric windows would be good but guessing bits needed from the elegance? Also I'm missing the ashtray inners, some places advertise for a drinks holder instead. Does it fit? Also drop down drink holders from either side of the stereo are these hard to come by etc?

Need to get fitted or semi tailered waterproof seat covers, are the semi tailored ones any good? Any makes recommended? Looked on ebay and hard to tell quality of material etc.

Thanks for reading

Mark