The post service is much better these days in Bulgaria and new post is processed much more quickly. We can receive mail from the UK in as little as just 3 days, parcels also. It's never more than 7 days anymore.
See more information on moving to Bulgaria: http://www.questbg.com/lifestyle/life/2247-moving-to-bulgaria-from-uk.html
How long does parcel post take to get to Nigeria from UK
How long does it take post to arrive from Brussels BELGIUM to the UK
I
UK city Hull. It will take about 4 hours, with a over stop at Heathrow
It depends if there is Traffic in the travelling.
5-7 days
It takes about 25 working days for the Hong Kong post to reach Parcelforce in the UK.
around 1 hour
2-3 weeks at most
6-10 days depending how you mailed it.
Postal mails (even ordinary, Par Avion) may reach fast from UK to Bulgaria. As there are many flights from London to Sofia per day. The question is from which part of UK is the mail and to what destination is to reach in Bulgaria. Overall 5-7 working days would be good enough. Priority and Courier mails reach faster.
Bulgaria and Poland are quite a ways away from the UK.