You already figured some of the information out yourself (the Schengenform, skipping the questions with an * and no fees).
More info can be found in de EU handbook for the processing of visa, which has a section on family of EU/EEA nationals (page 81> ):
http://ec.europa.eu/dgs/home-affairs/wh ... dex_en.htm -->
http://ec.europa.eu/dgs/home-affairs/wh ... ted_en.pdf
Your parents could most likely join you, them being non EU nationals joining an EU national (you, a British national) to an other EU country (Poland). If the Polish embassy would consider your parents as being dependant on you you might wish to check with the embassy. The handboook says:
Question no 2: Does the visa applicant fall under the definition of “family member”?
‘Core’ family members have an automatic right of entry and residence, irrespective of their nationality. Their right of entry
is derived from the Directive and the national transposition measures may not restrict these rights or the scope of ‘core’ family members. The following persons are defined in Article 2(2) of the Directive as ‘core’ family members:
• the spouse;
• the partner with whom the EU citizen has contracted a registered partnership, on the basis
of the legislation of any Member State, if the legislation of the host Member State treats
registered partnership as equivalent to marriage;
• the direct descendants who are under the age of 21 or are dependant as well as those of the
spouse or partner as defined above; or
• the dependant direct relatives in the ascending line and those of the spouse or partner as
defined above.
In order to maintain the unity of the family in a broad sense, Member States may extend the facilitations to so-called ‘extended’ family members, see Commission Communication COM(2009) 313 final.
AFAIK, "dependant" means you sometimes financially support them, or take care of them etc. They do not have to live with you. Perhaps that elsewhere in the forum a better explination can be found, and/or ask the Polish embassy what their view is.