Davyp you just have to plan it like a military manoeuvre.
an example of this would be a rather large sum i needed to get the wheels i have wanted for ages.
you must first let her know how much you love them by calling her over and saying "look at these darling what do you think they would look like on our car". AT first you will get this face
so you must show her lots of pictures until she really cant be bothered to walk over and look any more, then she should say yes, they look nice in that picture, just so she can have some piece.
Its at this stage where you must say "if we could afford them would you let me get some" she will smile and say no.
Now the important bit call her over and say look lets just get a price off the net now, i probably wont be able to afford them i know they will be expensive, but just lets have a look. Then just click on any set of Bentley wheels or something ridiculously expensive she wont notice its a different wheel as long as its round
Then as the price comes up you must drop your head and say oh sh!t, thats that over with then.
you must now over the next few weeks let her catch you looking at the wheels at every opportunity
it may take a while but at some stage over the next few weeks she will see the longing on your face as you gaze at them, and she will come over and put her hand on your shoulder and say, there just to expensive honey she will turn round with her back to you and smile her little head off, feeling really sad for you and your obsession.
Now you will be entering another phase were you randomly do stuff for her that you would not normally do,
like leave her with the remote,
tidy up before she normally makes you do it. A favourite of mine is to look through the holiday snaps on the computer with her and remind her how beautiful she looks next to the sea.
what ever you do dont make it obvious perhaps leaving her with the remote may set alarm bells ringing.
your now entering the last couple of phases.
After all you extensive hidden research into the cheapest possible price, you have got to hit her with it like a bomb going off and most importantly the word
Look! Look! i have found the wheels for a 1/4 of that usual selling price from a company closing down. I really cant believe it. its at this point you promise her everything that she has ever dreamed of, while pointing out there is only 2 sets left in stock.
And all your previous weeks of hard work will hopefully pay off.
This should work with almost any mod unless your Jonny C or Hurdy.