(Below) For comparison purposes:
1) The huge Type 43 destroyer - equipped with a greatly revised, "double ended" Sea Dart missile systems.  Cancelled in 1981.
2) An impression of the NFR-90 air defence frigate cancelled by the UK in September1989.
3) An Aster armed, stretched, air defence variant of the Type 23 frigate produced by Yarrow Shipbuilders in the early 1990's at the request of the MOD(UK).
4) An impression dating to 1996 of the UK variant of the CNGF Horizon frigate which was cancelled in early 1999.

(Below) Three pictures from November 1999 showing the early design concepts for the Type 45.  Particularly note:
1)  The flush-deck VLS Sylver missile silo 
2) The original Sampson radar design.
3) Harpoon SSM launcher tubes in a superstructure break amidships
4) Phalanx CIWS mount on the hanger roof
(Source: BAE Systems)

(Below) Various early-2000 artists impressions of the Type 45 Destroyer showing the design which was  presented for "Main Gate" approval in July 2000.  Compared with earlier designs there has been several major changes, note:
1) The VLS Sylver launcher system for PAAMS missiles has been raised one deck to give the capability in the future to fit a lengthened (Mk.41) silo should it become a requirement.
2) The redesigned spherical BAE Sampson radar array on the massive low signature foremast.
3) The bow which is clear of all mooring and anchoring equipment, no longer ramps down from the bridge to forepeak.
4) Anchor chains and mooring equipment remain on a mooring deck beneath main deck level behind openings in the hull which are closed – as on the quarterdeck – when the ship goes to sea. 
5) The ship’s boats concealed behind removable panels on both sides of the helicopter hangar.
6) The outward flare of the hull and tumble-home of the upper hull, superstructure and radar masts, all carefully designed to minimise the ship’s visibility to hostile radars.
7) The main superstructure block runs unbroken between the helicopter hangar and the bridge. 
8) Appearance of 4.5" Mk8 Mod 1 gun
9) The arrangement forward of the main gun, Principal Anti Air Missile System (PAAMS) silo and Harpoon surface-to-surface missile canisters mirrors that on the Type 23 frigate
10) The Phalanx CIWS amidships.
11) A Merlin helicopter is shown being operated, although this had become unlikely.
(Source: BAE Systems)

(Below) Artist's impressions released  in March 2001 of the Type 45 destroyer design after "Design Review 2".  Compared with the earlier pictures above note: 
1) Absence of Harpoon SSM canisters
2) Substitution of the Merlin HM.1 helicopter by the smaller Lynx HMA.8
3) Revisions to the superstructure and hull form, and a visible bow anchor
4) The weapons director platform "greenhouse" on the foremast

It's interesting to compare these pictures with the similar but updated pictures generated a year later, shown  further down the page.
(Source: BAE Systems)

(Below) Two pictures released in April 2001 of the Type 45.  Note the highly stealthy appearance and Merlin helicopter. The design revision seems to be very contemporary with that in the pictures above.
(Source: BAE Systems)

(Below)  This artist's impression of the Type 45 was first published  in July 2001, but was probably generated at the same as the pictures just above.
(Source: BAE Systems)

(Below)  Artists impressions of the Type 45, generated in February 2002 after Design Review 3.  Only minor changes have been made compared with pictures above, notably: the disappearance of  the weapons director platform "greenhouse" on the foremast, 02 deck amidships has been prolonged up to the aft mast/hanger structure, and the masts cleaned up with fewer aerial platforms, etc.
(Source: BAE Systems)

(Below)  The latest artists impressions of the Type 45, first published in June 2002.  Again only minor changes, most notably the re-alignment of the Sylver A50 modules in the VLS silo, visually there now seems to be space allowed for an additional centre line row of up to 3x8 cells - for a total of 72 Sylver cells - although this has never been claimed and internally the space may be used for access, services and other purposes.  However BAE Systems and the DPA have indicate that the Type 45 design can potentially take up to 16 land attack missiles such as Tomahawk, and the cells would presumably be fitted in to this space.