I really don't understand this thread. The Reading - Gatwick route could do with some enhanced signalling to reduce headways and some judicious line speed improvements. It could probably carry 2 fast(ish) trains an hour over the full length and two stopping trains per hour between Wokingham and Redhill (fast between Reading and Wokingham). With the increased frequency 3 coach Class 166s (possibly doubled in the peaks) would be adequate for the next decade.
Spending capital to electrify a route with such low usage seems like throwing money down a drain - especially with oil at around $40 a barrel a diesel train possibly has lower fuel costs than an electric one fed at 750v.
Oil is currently almost $50 per barrel and the price has been rising steadily since late January when it dipped below $30. Signs are that the upward trend is going to continue. What GWR is paying for its fuel will depend on a long-term hedged contract - as they don't want to get caught out by a sudden price spike if they can help it.
That said, I would agree there are places rather more like to get electrification money in the short term than the North Downs.
But if the claims Modern Railways made last year about the viability of the battery IPEMU were over the top and the sums actually can be made to stack up, offering the possibility of covering Bedwyn services and the North Downs, then who knows?
If they can squeeze out just a bit more than 50km range, then an IPEMU could cover Oxford-Banbury stoppers until that route gets wires. Hand Greenford shuttles to Chiltern or LO, develop a light rail solution for Marlow and bite the bullet on using an 80x on the Cotswold Line halts services - one of which is currently worked by a 180 anyway - and you would eliminate any need for Reading-based Turbos - send them west and GWR could probably release all the 150s that are due to remain past 2019, leaving just 158s and 165/166s on the books.
However, after the pledges from GWR to look closely at the IPEMU idea last year, it all seems to have gone very quiet on that front.