Is HND equivalent to Polish "Licencjat"?
No an English HND is not equivalent to a Polish degree. A Licencjat is the equivalent of a Bachelor of Arts degree in the UK. You're studying IT so that degree would be Bachelors of Science which is equivalent to the Polish Inżynier. Your diploma is not equivalent to Inżynier and will not count for much in Poland. To be honest employers even have some difficulty in understanding equivalence between a degree from an English university with Polish ones, let alone a diploma. It's worth doing the extra year or two for the degree.
The system of equivalence of degrees is worked out using the European Credit Transfer (ECT) system which is now recognised in Poland. Most of the major universities in Poland are now signed up to it, though many employers haven't heard of it.
You know that there's a difference in the UK between an ordinary/foundation degree and an honours one don't you? Ordinary Bachelors of Science requires 3 years full time study, Hons BSc requires four years but it's the more impressive qualification to have on your CV.
ECT points are awarded based on the number of hours of study required. Bachelor's degrees (also known as first cycle studies) are worth 180 - 240 ECTS (3 to 4 years full time, longer part time obviously). If you have the 240 points it's sometimes possible to get your BSc Hons degree recognised as equivalent to a Polish Magister. (Don't confuse the ECT points with the course points. A degree contains several courses that make up the content and each course is worth a certain number of points usually around 120 points a year, which will work out as 60ECTs).
Your HND is worth 120 ECTs. To have a Polish Inżynier you must have at least 180 ECTs.
I'd say that if you can possibly manage it carry on with your studies and go for the Hons degree. Your industry experience will certainly count in your favour but if your long term plan is to come back to Poland you should do so with the best qualification you can get. Poland is still a bit old fashioned and 'dokumenty' and the right kind of paperwork are still valued very highly. Good luck!
your level of English
I think you're being a bit harsh Roz. The standard of spelling amongst English native speaking students is pretty abysmal these days. I'm sure the OP is no worse than many of them. Apart from one spelling error on a commonly misspelled word I think his/her English is perfectly ok. Afterall he's studying a technicaI subject. Good basic communicative English is perfectly adequate. I think one has to allow a bit of leeway for people for whom English is a foreign language and who have often picked up their English along the way with very little formal tuition. To be honest even if the OP had learned English in school in Poland, that might well prove more of a hindrance than a help!