Let's be frank here, if it's where I think it is, you're in Borehamwood; the hotel probably says it's in Elstree to make itself sound nicer
I would say there are 4 viable stations for you to go to:
-Elstree and Borehamwood (why drive? Can't you park at the hotel for free? If you can, and you're using Oyster, buses are only £1.35, or included in any Travelcard you might have)
-Stanmore (it's not that far, and once again there's a nice pink bus to take you there run by Uno - it runs every 30-60 minutes throughout the day but is a Hertfordshire service so doesn't accept Oyster)
-High Barnet (bit of a walk to the bus stop for this one, so I'll let you off from driving)
-Edgware (Once again, you can take the bus for £1.35/free with Travelcard
)
Personally I would take the bus to Elstree and Borehamwood, take the Thameslink to Farringdon, cross-platform interchange to the Westbound Circle/H+C to Edgware Road, and change there to Notting Hill Gate (cross-platform half the time)
however this depends on the reliability of Thameslink services which is... low?
Either that or Northern line to Euston from HB/E'ware, then Victoria to Oxford Circus, then Central to NHG.
Or... Jubilee from Stanmore to...
*Wembley Park - change to Metropolitan faster service to Baker Street, then Circle/H+C, or back on the Jubilee to Bond Street and change to Central.
*Baker Street - change to Circle/H+C one stop to Edgware Road, then change to Circle/District to NHG.
*Bond Street - then take the Central as said above.
A *lot* of options I know!
My recommended is the first or last