Tinkerbellj - It's all a question of definition really.
The STRAW definition of peri-menopause
http://www.imsociety.org/downloads/email_downloads/2012_02_16_1773491/straw10.pdf which is also used by NICE does not define peri-menopause as happening until your cycle starts to vary by 7 or more days. The stage before this is referred to as the late reproductvie stage - which makes sense because you are still ovulating and could theoretically still conceive and get pregnant. Some change to hormones occur at this point as well as changes in flow and period length and in particular periods get shorter together.
Many women ( myself included) get/got more extreme pms symptoms at this stage - due to surges of and dips in oestrogen and progesterone some of which produce similar symptoms to peri-menopause. The difficulty is how to treat it and how it transitions into "official" peri-menopause - according to the medical definition. Regarding treatment - the definition helps to some extent in that once your periods start to go haywire oestrogen levels are definitely dropping and HRT helps to restore this and regulate the cycle as well as get rid of the most obvious troublesome symptoms.
Some women find that adding HRT during this time (periods still regular but very bad pms/hormone swings = mood swings) is not the complete answer because oestrogen sometimes is very high and when it drops it is very low and it's all so unpredictable - and this is acknowledged by gynaes. Someone recently reported Dr Currie's response to a question about this but I can't remember who and when!! The flushing is a problem though as some women start to get these very early - some of us are luckier and only get them when periods stop for a while ( in my case) and then adding HRT stops them.
If you're under 50 I would be tempted to try Qlaira but those of us who have an average age menopause or later can't take this past 50 - well not officially anyway.
A bit of a ramble .... but my take on it from what I've read.
Hurdity x