Any help on getting the required files for a (British) English dictionary would be appreciated as I have had little success with the set up of dictionaries.

I just set up an Australian one using the OpenOffice dictionary and it was reasonably straight foward.

Here's what I did, modifying it for a UK dictionary should be obvious:

1. Create a new Windows Forms project, add a spell check control and a MemoEdit to the form.
2. Download the OpenOffice dictionary files from here: http://wiki.services.openoffice.org/wiki/Dictionaries and add the en_AU.dic and en_AU.aff files to the project.
3. For both files, set the property: Copy to Output Directory to Copy if newer.
4. Add the following code to FormLoad event:

Dim auDic As New SpellCheckerOpenOfficeDictionary
auDic.Culture = New CultureInfo("en-AU")
auDic.DictionaryPath = "en_AU.dic"
auDic.GrammarPath = "en_AU.aff"

Dim auCustomDic As New SpellCheckerCustomDictionary()
auCustomDic.Culture = New CultureInfo("en-AU")
auCustomDic.AlphabetPath = "EnglishAlphabet.txt"
auCustomDic.DictionaryPath = "CustomEnglish.dic"

Dim sharedDic As New SharedDictionaryStorage
sharedDic.Dictionaries.Add(auDic)
sharedDic.Dictionaries.Add(auCustomDic) 

SpellChecker1.UseSharedDictionaries = True

 You also need these imports:

Imports DevExpress.XtraSpellChecker
Imports System.Globalization 

Run the project, type some text in the memo edit, right click it and choose spell check.