Caveat: I'm not writing as an apologist for Royal Mail's Tallents House
When the announcement of the rate increase was delayed until after Ofcom had deliberated (and after the Commons Committee had hauled in Moya Greene) somebody at RM HQ (London) decided that the new stamps could not be distributed despite being all ready. This, despite the fact that the airmail rates are not, as far as I know, governed by the regulator and that the only other stamp to be issued at that time (the Large Letter Jubilee stamp) is an NVI.
Dealers normally get their stamps up to a month in advance of the date of issue, but even that didn't apply. Couple that with the unprecedented demand online and by phone for all NVIs in the month between the announcement and the implementation, and the whole operation was overwhelmed. [The Tallents House operation includes collector sales, dealer sales, online sales, sales through their eBay shop, and retail sales in that a lot of small corner shops just phone up for extra supplies and get them next day).
We didn't get the new tariff stamps until over a week after the date of issue. I didn't get the Fashion stamps until 8 days after issue, and the Flags 2 days after issue. The people I deal with are working overtime and weekends and have done for 6 weeks or more. When I spoke to them last week they didn't know how many days (if any) they would get for the 4-day holiday at the end of this week!
So it is - as usual - the management. You can use philatelic.enquiries [at] royalmail.com as well as the phone.
As for what to collect, Royal Mail recognise that some people (still) want everything, although they (still) omit some stamps from their regular/standing order system. Cases in point: (a) only the 6 Feb Jubilee MS was distributed, not the self-adhesive stamp from counter sheets; (b) the Flag Post & Go stamp is not in the SO but the Pigs Sheep and Birds were. And of course 'visible change' doesn't mean changes to the 'invisble' security overprint.
Having recognised that completist collectors still exist RM decided 3-4 years ago that they were concentrating on niche/specialist collectors, and so there was the Kings & Queens series, the 'Species in Danger' series, and now the Railway series. They hope that by hooking collectors to those issues they may also attract them to other issues.
So the answer is either to stop altogether, or to stick to certain parts of the programme - perhaps only definitives or particular special issues. What causes most trouble is using preprinted album pages. They vary between producers so no one will be 'correct' or complete. What Royal Mail identify as different will not be the same as album and catalogue producers Lighthouse, Davo, SG, Michel, Scott regard is different and each of those will be different from the others.
You will find that gap-filling has become more expensive in recent years because dealers have stopped stocking new issues. Certainly when I've sold out of an issue, it's sold out, and for the last couple of years I have bought stock only for 2 new issue customers and - quite unnecessarily! - for use as postage.
But if I can help your gap-filling (mint or FDC) do send me a mail through the email button).
_________________
Ian Billings -
Norvic Philatelics GB stamps info:
http://www.norphil.co.uk - also /catalog for our ecommerce site, blog.norphil.co.uk, shop.norphil.co.uk and Ian_norvic on twitter
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And consider the popularity of collecting Czeslaw Slania's work, thus picking-and-choosing through the issues of Sweden et al. 
I have however recently taken stock of the situation and reckon that if QEII, with the best physicians in the world at her beck and call, manages to do what her mum did then RM will be bleeding me dry for another 20 years... 
