NHS doesn't offer rectal spacer as standard. With the accuracy of targeting and masking in modern LINACs, the chances of serious rectal issues is now low, and it's not considered worthwhile to offer it to everyone on the off-chance. Many radiotherapy units do buy a small number of rectal spacers for use in patients where rectal bleeding would be a serious issue, such as those on life-long blood thinners, IBS/Crohns, some diabetic patients, etc. It is often still offered privately, but the private price has rocketed in recent years for no good reason.
If you're having your RT in another country, I don't know how recent/modern the LINACs will be.
Fiducial Markers are part of the image guidance used by modern LINACs to accurately target the prostate, but this isn't the only way to do it. The image guided LINACs have a diagnostic X-ray head on the gantry too. This is used during aligning to take two X-rays at right angles to each other for aligning your prostate in the centre of the treatment beam, using the Fiducial Markers. Another way they can do it is to use the X-ray head to do a cone beam CT scan to make a 3D image of your prostate, bladder, and rectum, and this doesn't require Fiducial Markers. The cone beam CT scan is a higher X-ray dose (but less than a regular CT scan) and it takes longer to do, so they get fewer patients through the LINAC per hour, but it avoids the Fiducial Markers. Another way to do the image guiding is to use an MR-LINAC which is a combined MRI scanner and LINAC, but there aren't many of these in existence.
Much of this is going to depend what equipment is available where you are being treated.