An air compressor is one tool that I would hate to be without.
I have a small single cylinder 8 litre compressor in that lives in the van, then a 3hp V twin one of unknown tank size in the workshop.
The 8 litre one cost next to nothing from Lidl's about ten years ago, has had one hell of a life being used as a nail gun compressor, has lived out in all weathers, yet has proven to be 100% reliable. An 8litre tank size or similar, will be fine for your use, although obviously it will cut in and out a lot, which is thankfully something that the larger compressor doesn't do.
I tend to return from a ride, give the bike a quick blast over with air to remove most of mud, wash the bike down, use the airgun again to remove the water, spray the whole bike with duck oil, protecting brakes and suspension sliders/seals, then blast it again to remove the excess. If riding two or three nights a week, this is a very quick and easy option when time doesn't permit a deep clean.
The Lidl's one looks pretty much identical to this one.
https://www.amazon.co.uk/Clarke-Bandit-Litre-Air-Compressor/dp/B00EPPVAA0
I guess that this one could be a contender. If fails, you could just return it.
http://www.screwfix.com/p/impax-im201-24l-24ltr-compressor-230v/27926?kpid=27926&cm_mmc=Google-_-Product Listing Ads-_-Sales Tracking-_-sales tracking url&gclid=CNn2vtyd8tACFdU_GwodqQ8FaQ