Unless you are shooting "in the old fashioned way" then it won't just be a rifle equipped with its iron sights that you will need. Indeed that will be the least of your worries!
The "modern way" is to have certainly a telescopic sight (and mounts) plus maybe a moderator and a bipod.
Personally I don't like either moderator or bipod! But you may!
So accepting that, at the very least, you WILL need to buy a telescopic sight the next issue is mounts for the same.
Some rifles are fairly standard so large production runs give a scale of economy - Remington and Winchester - so will take cheap generic Redfield type mounts and rings.
Others - Mannlicher and Sako - will use mounts that cost considerably more such as the maker's own. The cost of these can be considerable!
However you may be very lucky! Stalking rifles are somewhat of a buyers' market in that secondhand they have poor residual values.
Try
www.bonhams.com for their end of July "Sporting Guns Sale" in London. You've just missed that of
www.holtandcompany.co.uk but they have another in September as do
www.southams.com in August.
Avoid certain Nottingham based auction houses. Mostly recycled offcasts being cleared out by dealers at the cheaper end of the trade.
Or that someone's "pride and joy" at auction or on sites like
www.guntrader.co.uk or the bigger dealers such as the very, very good
www.rmacleod.co.uk may be easily less than half the new price...and may even have mounts included!
Calibres that are deemed unfashionable such as 270 Winchester also can be picked up cheap. I've seen decent maker's rifles in that calibre for as little as £95! Nothing wrong with them...just no longer in fashion!
Optics. Buy the very, very best that you can and you'll only ever buy once. Again be careful with this but secondhand Zeiss and etc. from reputable dealers may offer a saving. But avoid the cheap rubbish that at £100 new price looks attractive but won't last more than a few months!
A good start? Buy a copy of the monthly "Gun Mart" and that will give contacts galore!
Lastly? Avoid being sold someone else's bizarre idea of the "ideal rifle". These things usually have sixteen inch barrels, moderators the size of the Queen Mary's funnels and a telescopic sight so powerful that Patrick Moore could view Uranus with it.
A good safe bet? A second hand Parker-Hale or BSA or similar quality factory made European rifle that takes generic Redfield "off the shelf" mounts.
Iron sights? I like them but really most shooting today will never ever require them. Barrel length in 6.5 x55? Don't go below about twenty-two inches.
The "extras"? I've managed quite easily with just the rifle, a spyglass and a knife! Oh an maybe my "piece"! But some seem to go out festooned like the gunshop Xmas Tree display on 24th December! Each to his own.