Is the /eə/ sound related to the /ə/ sound in British English?

Lately I'm into improving my English (UK) pronunciation. I'm using the IPA chart for such purpose.

I was wondering if there's any relationship between the ə sound and the several diphthongs that involves the "schwa" symbols, in the pronunciation (for example eə)

I mean is there some similarity to take into account?

The compound phonemes incorporating schwa (such as those in: near goat mature cure) do not in any way reproduce the schwa short vowel sound, although you might think they suggest it. They are just compound phonemes. No need to read anything into them.

http://teflpedia.com/Weak_form

The "similarity" is not coincidental; the vowel found in words like "care" is often transcribed as /eə/ because, historically, many people pronounced it like the sound [e] followed by the sound [ə], squished into one syllable. (The non-syllabic part was the [ə]; a more explicit transcription would be /eə̯/.) However, in modern Southern British speech, words like "care" are often pronounced with a long monophthong rather than a centering diphthong due to the phenomenon of "smoothing", so it may be better for you to aim for /ɛː/; at any rate, you should be aware of the existence of this pronunciation.

Here is a blog post about it by Geoff Lindsey: Smoothing, then and now