mikroBasic is a structured compiler with full IDE, Debugger, Libraries and examples, and a limitation of 2K Hex words for compiled code for the free download. Of course, 2K covers several PIC's totally. They have a great forum and lots of help.
https://www.mikroe.com/en/compilers/mikrobasic/pic/download.htm
Swordfish Basic is the best structured compiler on the market. The free download is the full compiler with a complete library and the best LCD/GLCD libraries around. It is for the PIC18 family only. The free download is limited to 256 variable bytes and no limit in Hex code size. The 18-pin PIC18's are totally covered by this limitation. It is also rumored that soon SF will be capable of running under Proteus/ISIS.