Magento 1.8 – Edit Display of Products in Catalog View Page

Okay, so have actually got quite a decent solution to this now using my second approach in my question. I'm unsure of the performance implications as of yet but here is what I have done...

<?php $categories = $_product->getCategoryIds(); ?>
<?php foreach($categories as $k => $_category_id): ?>
<?php $_category = Mage::getModel('catalog/category')->load($_category_id) ?>
<?php $ignoredcats = array(2,360,124,4); ?> <!-- add all category ID's here that we wish to ignore -->
    <?php if (in_array($_category_id, $ignoredcats )){ ?>
        <?php //do nothing ?>
<?php } else { ?>
<?php if($_category->getIsActive()): ?> <!-- make sure the category is active first -->
    <p>View more <a href="<?php echo $_category->getUrl() ?>/filter/<?php echo strtolower ($manufacturerName = $_product->getAttributeText('manufacturer')) ?>" onclick="_gaq.push(['_trackEvent', 'Internal Linkage', 'Product Back To Links', '<?php echo $manufacturerName = $_product->getAttributeText('manufacturer') ?> <?php echo $_category->getName() ?>',, false]);"><?php echo $manufacturerName = $_product->getAttributeText('manufacturer') ?> <?php echo $_category->getName() ?></a> from Showermania.</p>
<?php endif; ?>

This will then output something like the following screenshot shows but by specifying the category ID's in $ignoredcats will only render for the categories of my choice.

I can then style or modify the output accordingly. You could alternatively only output this for allowed categories instead of else not allowed instead if wanted.

Does the job effectively for me currently but yet to notice any performance implications or any issues that will arise from this.

You can do this with some simple CSS. You should remove the register and sign in links from the template but this will have the desired effect:

/* Remove the register & sign in buttons */
.header-bottom-content ul.link-bottom {
    display: none;
}

/* Reduce the size of the search box */
.form-search input.input-text {
    width: 250px; /* Change to desired width */
}

Simply add it at the bottom of your themes CSS file. You'll want to update width: 250px; to the desired width of the search box. You will end up with a large white gap between the search box and the basket button which isn't ideal.