12 450s are booked regularly throughout the SWT network, so I'm afraid they are not notable at all. To give you an idea, here's all the SX 12 450s due through Waterloo up until 7pm:
In
0455 from Southampton Central, arr 0634
0612 from Alton, arr 0718
0630 from Haslemere, arr 0734
0550 from Portsmouth Harbour, arr 0743
0644 from Alton, arr 0749
0707 from Woking, arr 0754
0654 from Basingstoke, arr 0757
0543 from Portsmouth Harbour via Eastleigh, arr 0759
0706 from Basingstoke, arr 0804
0710 from Haslemere, arr 0809
0732 from Woking, arr 0817
0714 from Alton, arr 0820
0746 from West Byfleet, arr 0824
0724 from Basingstoke, arr 0827
0623 from Portsmouth Harbour via Eastleigh, arr 0832
0747 from Woking, arr 0834
0711 from Havant, arr 0839
0802 from Woking, arr 0844
0744 from Alton, arr 0850
0713 from Portsmouth Harbour, arr 0853
0655 from Portsmouth Harbour, arr 0911
0847 from Woking, arr 0938
0939 from Haslemere, arr 1040
1024 from Basingstoke, arr 1136
1039 from Haslemere, arr 1140
1703 from Clapham Yard, arr 1713, ECS
1624 from Basingstoke, arr 1734
1450 from Poole, arr 1736
1545 from Portsmouth Harbour, arr 1743
1742 from Clapham Yard, arr 1752, ECS
1615 from Portsmouth Harbour, arr 1754
1644 from Alton, arr 1759
1555 from Portsmouth Harbour via Eastleigh, arr 1808
1624 from Portsmouth & Southsea, arr 1814
1804 from Clapham Yard, arr 1814, ECS
1656 from Havant, arr 1827
Out
0650 to Woking, ECS
0725 to Woking, ECS
0745 to Portsmouth & Southsea
0753 to Alton
0802 to Woking, ECS
0809 to Portsmouth Harbour via Eastleigh
0812 to Clapham Yard, ECS
0813 to Basingstoke
0815 to Haslemere
0818 to Northam Depot, ECS
0828 to Clapham Yard, ECS
0830 to Clapham Yard, ECS
0842 to Basingstoke
0845 to Portsmouth & Southsea
0845 to Clapham Yard, ECS
0853 to Alton
0854 to Clapham Yard, ECS
0900 to Portsmouth Harbour
0916 to Haslemere
0930 to Portsmouth Harbour
0949 to Clapham Yard, ECS
1056 to Clapham Yard, ECS
1152 to Clapham Yard, ECS
1212 to Clapham Yard, ECS
1453 to Alton
1730 to Portsmouth Harbour
1753 to Basingstoke
1755 to Alton
1800 to Portsmouth Harbour
1802 to Woking
1810 to Portsmouth Harbour via Eastleigh
1812 to Basingstoke
1823 to Basingstoke
1830 to Portsmouth Harbour
1832 to Basingstoke
1846 to Portsmouth Harbour
Unfortunately, a number of the Waterloo - Poole/Brockenhurst services are booked 4 450, but on the bright side, the 1235 Waterloo - Weymouth is now booked a 5 444 instead of a 4 450.