Free BMD gives the marriage of Frederick Jackson and Eliza Beard in the December quarter of 1843 in Dunmow, Essex. Vol 12 Page 157. From this you can order a marriage certificate from the General Registry Office.
Free BMD is an excellent resource for find what is in the Registry Office from 1837 onwards. Free Reg and Free Cen can also be helpful for a census or a parish register. They are being transcribed by volunteers, Free BMD is pretty well covered, but still getting bits put in, Free Cen and Free Reg are behind. Those volunteer transcribers have and are doing a brilliant job.
As a beginner you may not have Ancestry or Find My Past but you might like to look at Family Search
https://www.familysearch.org/search/ It is free to join and has masses of records.
You may know anyway!!
Good luck