possibly, my local model place had peco 'large' E/F points at around £13 each, can get them mail order cheaper, including postage, but I only ever got two and wanted them "now" so paid a bit more.
are you using finescale C55 or the 'normal' C80 stuff? asking since the cost is basically the same but the C55 does look better.
personally never used ebay, mostly due to paypal 'issues' in the past, but many find it fine.
you will be amazed how far cash actually goes, though it may not seem it, in N gauge
e.g. a full Class 225 rake costs maybe £90 for the loco & DVT, the coaches maybe a tenner each, so the full rake is under £200. in OO the locos are a lot cheaper, the stock a lot more.
track is about the same, but the plan you have won't be that expensive, plus build it in stages

btw there is no harm in replacing points with plain track, then later lifting it to put the point in, e.g. adding the fiddle yard bits later saves a bit of cash until you actually need the space.
but for a tight budget (which I've worked to before) the most important thing is planning what you need and when, then sticking to it
