Fly to Sofia international airport (all year round).
Fly to Plovdiv airport (during ski season).

For flights from all UK airports - check out :
www.wizzair.com
www.easyjet.com
www.aerlingus.com
Www.ryanair.com
www.cheapflights.co.uk
www.charterflight.co.uk
www.justtheflight.co.uk
www.britishairways.com
www.maritravel.co.uk
www.lastminute.com
www.travel.kelkoo.co.uk
www.skyscanner.co.uk
www.expedia.co.uk

For availability and price we find WIZZ AIR or EASYJET the best.

For good car hire we have previously used www.bulgariarentalcar.com although there are many other companies and we suggest doing some research.