Just Started Collecting UK Half Pennies

By far and away the most difficult Half Pennies UK that may?, if you are lucky, are the
high tin alloy Half Pennies 1689 - 94, covering the reigns of James 11 and William and Mary.
I have never seen an example in VF or better; such coins cost $ thousands.

They had a copper plug to help address a counterfeiting problem, bigger problem was the genuine coin itself, with bi-metallic corrosion.

Better and more practicable to start with a type set, then a date set, with bronze coins starting from 1860 through 1970, but beware - there is almost a galaxy of minor varieties, especially more common in the Victoria young head series 1860-94.
Some of these varieties are not identifiable if they are very worn.
You will become a numistmatist, not just a coin collector, if you can manage this series well.

to CCF

Christopher Perkins - Collectors Coins Great Britain 2018 is available as a Kindle eBook, substantially cheaper than the physical book.
Derek Allen's Standard Guide to Grading British Coins, also available for Kindle
free info https://halfpennyvarieties.wordpress.com/ - an excellent reference

If you're looking at varieties of bronze halfpennies then https://www.commonwealthcoins.net/b...ional-bronze is the most up to date reference book on halfpennies that I know of.
Not sure what the good references are for copper and earlier.
For decimal halfpennies I'm not sure if there are any detailed reference books.