Is the Vintage event at Cookham on the 16th May part of the De May Series and if not why not...?

Seems to be according to the Events Page

Yes, I believe it is.
I have been roped in as race officer! 
Now I have acquired 'Tiercel'  no. 901 I will try and get her out sailing as well - with some nameless rockstar in control perhaps.
We at Cookham are all ready and excited about this weekend - so make sure you put it in your diaries.

If you check out the calendar on the 'Vintage' section the ONLY exception is Thames Vintage regatta on 18th July. All other events listed, at present, are De May series (but not all are exclusive).
Further to this, the MROA is keen to promote any Merlin activity and clubs may use this page to advertise specific vintage events other than De May Series.

Yes it is, it is our first year holding it and, as Pat syas, we are quite excited about it. We are hoping that ots of you will come and join in.

Does the Guy Pearce Trophy then become the Cookham Vintage Merlin Trophy?  I also know some Rock Stars who also own vintage boats.... 

Rock stars.. get it (they sail on the river)

No, it is a seperate trophy but the Guy Pearce will be run as part of the 3rd race of the Vintage trophy.

I see and what time will be the first race...?

OK - this is not the official NOR but this how I see the weekend going:

First race for the vintage De May trophy start Approx 11.30 to give time for travellers to rig in a leisurely way. Race to last about an hour - so back for lunch.

Second race after lunch - about 13.45 so as to finish in time for the Guy Pearce Trophy race - due to start at 3pm

Guy Pearce Trophy will be the 3rd points race in the de May series and will also be open to all Merlin Rockets. Results will be calculated using the MROA handicap system - so vintage boats could easily walk off with plenty of glassware! I think results for the De May series should be calculated excluding the results of other boats not in that series. If we have a very big entry we might consider two starts for the Guy Pearce event - with the De May boats starting separately.

Then it is back for tea and de rig, by which time the sun should be approaching the yardarm and the evening entertainment can begin.

Sunday - the start for the Cookham Shield and Silver Tiller points is at 11.00. We confidently expect more than 20 boats so it should be run on the group system. No handicaps for this but, of course, all merlins are welcome and river sailing being what it is vintage boats can do very well. So please come and enjoy a great weekend at our club!

I know of one vintage Rock Star who is planning a clean sweep...

I spoke to Roger (Daltry) and he is up for it but a crap sailor apparently - so I withdrew the offer. Waiting for Mick's agent to come back to me, Cookham is much nicer than Mustique in May don't you think?

No, Gary Glitter - he is on yard duty... arf arf