Most successful swaps chart for contestants who no dealed every offer and swapped at the end:

All 2006:

1 October 24th Valerie Won £9,999.90 more than box swapped away Winnings: £10,000 swapped from 10p
2 February 27th Gary Won £5,000 more than box swapped away Winnings: £15,000 swapped from £10,000
3 July 1st Janelle Won £4,999.50 more than box swapped away Winnings: £5,000 swapped from 50p
4 September 20th Khanny Won £4,995 more than box swapped away Winnings: £5,000 swapped from £5
5 June 8th Becca Won £999.50 more than box swapped away Winnings: £1,000 swapped from 50p
6 April 15th Gabrielle Won £950 more than box swapped away Winnings: £1,000 swapped from £50
7 December 5th Maggie Won £495 more than box swapped away Winnings: £500 swapped from £5
8 January 23rd Ann Won £249.50 more than box swapped away Winnings: £250 swapped from 50p

The banker supplemented Gabrielle's winnings by £1,000 to increase them to £2,000 because she said she was giving the money away to charity. No one has yet won 50p, but it has been swapped away 3 times!

Most successful swaps for dealers chart:

All 2006

1 December 4th Ned Swapped £250 for £75,000 (£74,750 gained) Winnings: £15,000 Dealt at 5th Offer
2 December 7th Mike Swapped 1p for £20,000 (£19,999.99 gained) Winnings: £26,500 Dealt at 3rd Offer
3 June 6th Suzanne Swapped £500 for £3,000 (£2,500 gained) Winnings: £47,000 Dealt at 4th Offer

On June 6th 2006 there was no cash opening offer and instead Suzanne was offered the chance to swap her box. She accepted this offer and swapped Box 19, which contained £500 for Box 3 which contained £3,000. She dealt at the fourth offer for £47,000. Another 8 contestants have been offered the swap at the first offer, namely Bianca, Naqiyah, Sarah, Alan, Rhona, Steve, Dawn and Mike, but only Mike accepted the offer and swapped his box, swapping box 2 which contained 1p for box 11 which contained £20,000. Mike dealt at the third offer for £26,500. On December 4, 2006, Ned accepted the swap at the third offer, swapping box 9 which contained £250 for box 22 which contained £75,000. Ned dealt at the fifth offer at £15,000.

Little correction - Gabrielle swapped away the £50, rather than 50p.

It's so annoying that none of the good swaps are as good as the bad ones are bad...Valerie's felt brilliant, but wasn't really anything compared to the horror of Barbara's.

And Ned dealt at the 5th offer.

UPDATED:

Most successful swaps chart for contestants who no dealed every offer and swapped at the end:

All 2006:

1 October 24th Valerie Won £9,999.90 more than box swapped away Winnings: £10,000 swapped from 10p
2 February 27th Gary Won £5,000 more than box swapped away Winnings: £15,000 swapped from £10,000
3 July 1st Janelle Won £4,999.50 more than box swapped away Winnings: £5,000 swapped from 50p
4 September 20th Khanny Won £4,995 more than box swapped away Winnings: £5,000 swapped from £5
5 June 8th Becca Won £999.50 more than box swapped away Winnings: £1,000 swapped from 50p
6 April 15th Gabrielle Won £950 more than box swapped away Winnings: £1,000 swapped from £50
7 December 5th Maggie Won £495 more than box swapped away Winnings: £500 swapped from £5
8 January 23rd Ann Won £249.50 more than box swapped away Winnings: £250 swapped from 50p

The banker supplemented Gabrielle's winnings by £1,000 to increase them to £2,000 because she said she was giving the money away to charity. No one has yet won 50p, but it has been swapped away 3 times!

Most successful swaps for dealers chart:

All 2006

1 December 4th Ned Swapped £250 for £75,000 (£74,750 gained) Winnings: £15,000 Dealt at 5th Offer
2 December 7th Mike Swapped 1p for £20,000 (£19,999.99 gained) Winnings: £26,500 Dealt at 3rd Offer
3 June 6th Suzanne Swapped £500 for £3,000 (£2,500 gained) Winnings: £47,000 Dealt at 4th Offer

On June 6th 2006 there was no cash opening offer and instead Suzanne was offered the chance to swap her box. She accepted this offer and swapped Box 19, which contained £500 for Box 3 which contained £3,000. She dealt at the fourth offer for £47,000. Another 8 contestants have been offered the swap at the first offer, namely Bianca, Naqiyah, Sarah, Alan, Rhona, Steve, Dawn and Mike, but only Mike accepted the offer and swapped his box, swapping box 2 which contained 1p for box 11 which contained £20,000. Mike dealt at the third offer for £26,500. On December 4, 2006, Ned accepted the swap at the third offer, swapping box 9 which contained £250 for box 22 which contained £75,000. Ned dealt at the fifth offer at £15,000.

Very true, and we haven't even had 10 successful swaps yet in terms of contestants who have no dealed all the way and accepted the swap at the end unlike the Top 10 most unsuccessful swaps.