Private Eye/Cyclops 589 Xmas Pseudding

It’s Christmas! So it’s the giant 21×21 sized Eye crossword with some special feature.

This puzzle has a preamble:

Running clockwise around the shaded squares, starting top left, are two sentences from a 2016 ‘Pseuds Corner’ entry. Cuts have been made to fit the quote in the grid. One clue, lacking a definition, leads to the perpetrator’s name.
The 52 letters of the quote not intersecting with clue answers are:

AAAAAA EEEEE FF H IIIIII K LLL M N OOOOOO PPP RRRR SS TTTTTT U WWW Y

For solving this beast I began on a day when nothing else was going to distract me, and spent far too many hours slapping in clues, scratching my head and chuckling.
I had read all the way down to 28A ELECTRIC EEL before reaching a “write in” clue to begin, and as this was near enough in the middle I found the grid fill proceeded methodically from there kind of spiralling clockwise from the centre.  So I did not cross many of the perimeter shaded squares till later on.  I had almost forgotten the preamble when I hit 7D and briefly wondered where was the definition in the clue before realising this must be the one and getting the LLEWELYN part from the crossing letters and the anagram fodder, so I was primed with a Pseud-like author well before tackling what the quote might be.  I thought inclusion of bars showing word length in the perimeter was a great help.  Without those, getting the quote would have been very difficult indeed.
The first part of the quote was the first to fall into place.  Despite the triple unknown squares on the top right hand corner the word could really only be RELATIONSHIP
I had about 10 unanswered clues, mostly of the left-hand edge, when I sorted out the rest of it and needed to try slotting unused letters in to work out what the last words there could be – they eventually appeared as TALK TO ME which gave me valuable crossing letters for some of the last unanswered clues.
That last stretch did take a while: I had about 10 unanswered clues including 12, 15 and 19 so those extra crossing letters really helped.
The very last clue answered was 42/10 EVEN SCORE.  I just couldn’t see this, mainly because the phrase is surely “even the score”.

Just to be clear here is the quote from the shade squares and the position of the non-intersecting extra letters:

ITS IMPORTANT TO HAVE A RELATIONSHIP WITH YOUR INTERIORS AFTER HALF A BOTTLE OF WINE I WANT MY WALLPAPER TO TALK TO ME
IT  I P R A T  O  A E   R L TIO S I  W T  Y U  I T R O S AF E  H L  A  O T E  F  I E   WAN  M  W L P P R  O  A K  O  E

Cor Blimey! I wish I could get that effect from a little half-bot.
My wallpaper doesn’t utter a whisper until I’ve had several pints to wash down a couple of tabs of acid.

I dug out the copy of the mag from the teetering pile of old Eyes languishing in the corner of my study.  It was in Eye 1414 8-March 2016.  The full quote is:
It is really important to have a relationship with your interiors and to be attracted and seduced by them. After half a bottle of wine I want my wallpaper to talk to me.  Wallpaper really gives a big sense of soul to a house.  Bare walls are very Roundhead and an expression of low self-esteem … [continues]
From The Times

Phew