I'm an editor and proofreader.
Proofreading tends to be the last editorial step before a book is published. First you may need a MS critique or a developmental edit. You'll definitely need a copyedit.
Have you had any beta readers? That might be a good first step.
If you're hoping to be picked up by an agent, you may not need to worry about professional editing first, though some of my clients ask me to polish the first three chapters/10k of a book to send to an agent.
If you're self publishing, I'd suggest a MS critique then a copyedit. The first will pick up any 'bigger picture' issues with your book, if there are any. Copyediting focuses on the text at a sentence level, ensuring consistency of SPaG as well as consistent POV, tenses, timeline, checking that plot threads are tied up, that language is appropriate for the era you're writing about, that everything make sense and your text flows well.
Ask an editor for a sample edit of 1000 words so you can see how they'd edit your book. That's really important.
I'd check out the CIEP Directory for trained, qualified editors/proofreaders - www.ciep.uk/directory/directory-search - using the keywords 'historical fiction'. .
Costs will vary. I'd expect to edit about 2,000 words per hour for an indie author, so that's 57 hours for a book of 114k. The CIEP's suggested minimum rate is about £26/hour for copyediting, IIRC, so a good editor won't be cheap.
Have you joined ALLi? V good for indie authors: www.allianceindependentauthors.org/
Good luck! If you have any questions, do PM me.